The Water Management Society

WMSoc Questions and Answers

The advice offered in this section has been drawn up in the spirit of general guidance. If there is any doubt, in any case, expert advice must be sought.

Q1) Chemical Levels in Water Systems

HSG 274 part 2 and other guidance aims for 0.5 ppm minimum residual chlorine in drinking water and at sentinel points. Monochloramine can be used as a water disinfectant and sometimes there can be a mix of both in the water. Also chlorine dioxide dosing can be in use. Therefore:

1/ Is it valid, measuring free chlorine when only dosing with Sodium Hypochlorite that this gives a trustworthy measurement of disinfectant, assuming a quality test kit is being used?

2/ Does measuring free chlorine alone give a measure of disinfectant effectiveness where it is only monochloramine or only chlorine dioxide that is being used as a disinfectant or does one have to measure these individual chemical levels at storage and sentinel points?

3/ If it must be individual levels of monochloramine or chlorine dioxide respectively - what should the target range of levels be at storage and sentinel points?

4/ Where only monochloramine or only chlorine dioxide dosing is being used - would this show up on swimming pool type test kits that are used to measure free chlorine and could this lead to false information where free chlorine was not detected but indeed there was enough of these disinfectants there?

5/ What is the best way in the field of measuring free chlorine, monochloramine and chlorine dioxide in domestic water systems?

A1) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q2) Spray Chlorination

Can you give me any formal approval of the spray chlorination method on cold water storage tanks (not including down services)? The guidance doesn’t talk about this method nor does it say that it isn’t allowed.

A2) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q3) Disinfecting New Hot Water Generators

When we disinfect new hot water generators do we have to disinfect the entire distribution network including the cold water services? There may be a situation where, when disinfecting, there is cross contamination through mixer taps.

A3) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q4) Disinfection of Water Supply Systems

Could you please confirm if there is a British Standard or ACOP covering the disinfection or sanitisation of water supply systems?

A4) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q5) Mains Water

What is the procedure for chlorinating mains water systems?

A5) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q6) Disinfection of Down Services

When disinfecting the down-services of a building is it acceptable practice to neutralise the chlorine and leave it in non-potable water?

A6) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q7) Disinfection of Cold Water Storage Tanks

How do I disinfect a cold water tank in a hotel?

A7) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q8) Neutralising Free Chlorine

When sodium thiosulphate is used to neutralise free chlorine in water will it also help destroy combined chlorine, i.e. chloramines?

A8) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q9) Silver-Hydrogen Peroxide

I am looking for some advice on a new product.

A salesman has approached us from a company offering a product for the use in chlorinating cold water storage tanks. Apparently, this product negates the need for physically cleaning the tanks too; I cannot see how this is possible.

We are wary of any product like this that contains silver traces, as silver is basically a poison. At the minute we would only use Sodium Hypochlorite for the chlorination of cold water storage tanks.

Is this product recognised as an acceptable product to be used in the control of legionella under L8?

A9) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q10) Chlorine Dioxide in Schools

We have chlorine dioxide injection into water systems serving schools. The levels of treatment are maintained automatically via redox units. Once these dosing systems are installed, do the taps in the system still have to be turned on for a short duration every week?

In particular, during school holidays when the premises are hardly used, would it be a requirement to continue turning on the taps every week? Does dosing the water ensure that the water quality remains an acceptable quality?

If the water is being dosed continually with chlorine dioxide, is there still a risk of legionella growing in the system?

A10) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q11) Descaling of Shower Heads in Primary Schools

With regard to the cleaning of showerheads, if I was to replace the showerheads with brand new ones four times a year, am I complying with the regulations?

A11) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q12) Tanker Cleaning

Please could you offer some advice, I have a client who has asked what is the legal requirement, if any, for cleaning out water transport tankers – C6000gals. My initial thought was to treat them as normal CWST and offer a chlorination once per year, with a 6 monthly inspection. To clean I would offer fogging and limit the entry due to confined spaces etc.

A12) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q13) Chlorination Success

a. What is the success criteria for a chlorination?

b. I've noted that the industry standard is "no significant increase" from incoming mains but am unable to find where this comes from.

c. Additionally, Which guide states that samples are to be taken 48 hours post disinfection.

A13) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q14) Void Properties

I have recently been contacted by one of our maintenance managers who has requested some advice and guidance on the flushing and disinfecting of void properties that have gas combi boilers. When a property has been void for more than 30 days our current policy is to flush and disinfect the complete water system including the Cold Water Storage Tank (CWST), calorifier and all relevant pipework and fittings. For the above task our contractor is required to supply a certificate detailing the type of chemical used, contact time etc. and other details. We have however a large number of properties, mainly flats, in which combi boilers have been installed. On occasions some of these properties can be void for several months and I am seeking some advice on the best method of disinfecting the water system before these premises are re-allocated to new tenants. Our problem regarding combi boilers is: 1. Thermal flushing is not possible in void properties as the existing gas service has been capped. The gas service can’t be reinstated until the new tenant has taken possession of the premises and has contracted with a new gas service provider. Even if thermal disinfecting was possible, it would only apply to the hot water pipework. 2. For normal domestic type combi boiler installations, chemical disinfecting is currently not possible as there is no facility for applying chemicals. Any chemical application would most likely need to be applied under pressure at a point in the main water supply to the combi boiler. My understanding is that a water system that has no stored water and does not have a potential to generate water aerosols would normally be defined as low risk. However if this type of system is left unused for several months this greatly increases the risk of Legionella proliferation. Draining down a combi system is not always feasible, so would flushing alone, prior to a tenant taking possession of the property suffice? I have suggested that for future combi boiler installations we may have to install a tail in the pipework of the main water supply to enable the disinfecting of the water system. Any help or guidance would be greatly appreciated.

A14) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q15) Disinfection During Use

As a tenant in an office building, our landlord informed us that he had pulled through a food safe disinfectant to the whole drinking water system while staff are on site. He had not informed us that he would be doing so. Is this acceptable practice? Is there any risk associated?

A15) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q1) Combination Boiler Flexi Filling Loop

I advise any customer with a temporary braded flexi filing loop on their combination boiler to disconnect it. Some of my customers have been told by their plumbers that if it contains a check valve then it can stay on. Please advise.

Q1) Towel Rails

I have a question regarding a residential block of some 75 flats, currently served by two massive calorifiers that are now well past their sell by date, it is our intention to replace these with direct fired hot water generators. The system currently includes towel rails that are connected to the open hot water system. We have been advised that the towel rail should not be connected to the water system and that this is in accordance with currently imposed regulations. I have been through the regulations and cannot find any reference to this claim. Can you help?

Q2) Refurbishment of Accommodation Block

We are refurbishing a large accommodation block, which has been empty for a number of months.

The refurbishment will include the stripping out of plumbing, heating, showers, tanks etc.

What tests do you feel are required to check for legionella prior to work commencing (if any) and what precautions should be taken during the work.

Q3) TMV Placement

My understanding is that a TMV is fine to supply a non-TMV mixer tap as long as the cold supply to the mixer tap is getting turned over? Even though it would be best practice, there would be no need to rip out an existing TMV and replace with a TMV Tap unless deemed necessary by risk assessment?

Q1) Antimicrobial Fill Packs

Are there any concerns about the use of Antimicrobial Fill Pack for Cooling Towers?

Q2) Idle Cooling Towers

If a cooling tower or evaporative condenser is standing idle, how often should it be put into operation?

Q3) Cooling Tower Systems

Is there a concern using bromine with acidic scale control formulations?

Q4) Cooling Tower Systems Chemical Storage

Is there a concern if drums of bromine tablets are left open?

Q5) Cooling Tower Systems Chemical Storage

Is it necessary to place chemical drums and dosing tanks in bunds?

Q6) Cooling Towers

I am H&S consultant to a company who operate a small cooling tower installed in 1987. Passage of time and changes of staff mean that the current maintenance regime is something that has been passed down by word of mouth over the years and I am concerned that the practices followed may be inadequate particularly in respect to control of legionella.

I have been unable to trace successors to the manufacturers to get advice from them. Can you make suggestions as to whom I should contact to get information that will help us to confirm that current practices are adequate or, if not, to set up appropriate treatments and records?

Q7) Removal and Decommissioning of Cooling Towers

Is there a procedure for the removal and decommissioning of cooling towers? Are there any legal aspects we need to be aware of?

Q8) Cooling Systems and the Powers of EHOs.

The Environmental Health Officer (EHO) for my area of London has requested daily visits to monitor a cooling tower on a site we maintain. Can you advise on recommendations with regard to monitoring and testing intervals?

Q9) Biocides In Cooling Systems: Chlorine Activated Bromine Micro-Organism Control Mechanism

I have a client in the City of London where we are running a chlorine activated bromine micro-organism control mechanism.

The system has on line filtration, redox and conductivity control. Generally culture slide results are less than 1x103 and 1x104cfu/ml, consecutive months testing for legionella has not detected any contamination. Should I be dosing a secondary biocide to act as a surfactant? According to the manufacturer's handbook, chlorine activated bromine programmes will penetrate bio film. By not dosing a secondary biocide would I be leaving myself open to criticism?

We are also dosing a product for corrosion/scale control which has dispersant properties.

Q10) Cooling Tower Systems

Is there a concern using bromine with non-oxidising biocides?

Q11) Safety Data Sheets

How important is it to display safety data sheets in locations where chemicals are stored or used?

Q12) Cooling Tower Systems Supporting Documentation

Is it necessary to place a copy of all support documents such as the schematic diagram, safety data sheets, cooling tower registration form in a cooling tower log book?

Q13) Wet Scrubbers

Do you have any guidance on the control of Legionella in wet fume scrubbers used for the removal of odours?

Q14) Endoscope Inspection of Cooling Towers

We have a client with two cooling tower systems on site. We have advised the client that they need to prove the tower cleanliness, and they have agreed to carry out a 6 monthly endoscope inspection on both towers. They have advised that the towers are not able to be brought offline completely as they are required to be in service 24/365 and they have no outage planned within the next 6 months.

They have said that they are able to isolate the fans on the tower, but must keep the water circulating throughout the system and over the tower distribution. What are your thoughts on carrying out an endoscope on the tower under these conditions? We have some initial concerns over the quality of the inspection photographs as the packing will have water flowing over it. We also have concerns around doing an inspection on a live and recently chlorinated system. Is this an accepted method of carrying out an endoscope inspection and are there any considerations that we need to take into account when discussing this with the client?

Q1) Healthcare Calorifiers

Can you confirm that hot water storage vessels (calorifiers) should remain on at all times in healthcare premises?

Q1) Multi-Occupancy Buildings with Individual Hot Water

In a high-rise block of flats with individual hot water systems in each flat, how many hot water taps should be checked and how often?

Q2) Care Home Hot Water Systems

A Care Home has been advised to keep water temperature down to 43-44°C at the hot taps, to prevent scalding. The owner is aware that water must be stored at 60°C and recirculated at 55°C to minimise potential problems with Legionella in the pipework between any temperature control valve and the outlet(s). How does he reconcile the apparent differences in demands?

Q3) Hot Water Temperatures in Care Homes

What hot water temperatures do I need achieve in a Care Home I am responsible for?

Q4) Tanked Water Testing Frequency

Can WMSoc supply a set of guidelines that clearly outline the frequency required when having analysis conducted on drinking water supplied from a tank?

Q5) Dead-Legs

Would an unused washbasin or shower in a vacant room be a dead leg?

Q6) Dead-Legs

The water supply to feed anyexpansion tanks and closed system pressurisation units are infrequently used. What advice could you give us on the way to approach this when carrying out a Legionella Risk Assessment? Do we treat the supply to these tanks as dead legs?

Q7) Calorifiers

Why is it, that the hot water secondary water always returns to the centre of the calorifier and not to the base. This would eliminate the use of de-stratification pumps.

Q8) Hot and Blended Water System Temperatures

Can you tell me the required Hot Water and Blended Water Temperatures in building systems?

Q9) Calorifiers and Water Temperatures

Please could you help? I have a client who operates a hot water system, which is pumped and reaches 50C on the calorifier return during the week. At weekends the system heating is turned off, but water can still be drawn to outlets if there are workers on site, but these will be few in comparison to the usual workforce.

I have been asked whether this is acceptable and find it hard to judge in view of the following: -

Previous HSE guidance (L8 2000, paragraph 154) indicated that periods of less than 1 week may be acceptable, however that was in the context of a shutdown not a weekend and there is nothing equivalent in HSG274 part 2.

Q10) Calorifiers

Please could you comment on the following?

I have a client who has several older style calorifiers, which have a pumped ring main returning to the middle of the calorifiers.

Would it be acceptable to re-pipe the return water into the cold water down service feed provided non-return valves are fitted? Or should I insist that shunt pumps be fitted?

Q11) Electric Water Heaters

We have a problem in so much that when taking temperatures of small electric water heaters, the delivery temperature is often 46 - 49C, possibly due to a recent use and insufficient time to allow the water to heat up again.

As there is no adjustment on these, how much time should be left from its last use which could have emptied it until a temperature is taken? How much under the 50C is acceptable?

Q12) 'Fortic' and Other Combination Water Heaters

I have recently carried out a risk assessment and compiled a scheme to minimise the risk from legionella, for a housing association. The property is sheltered accommodation for the elderly where the occupants have their own flat/bedsit.

Hot water is provided in each flat/bedsit by individual Fortic tanks.

As the temperature in the cold section in each of these tanks is around 36C, usage could be small and stratification in the hot water part of the system could occur, I have identified this as a high risk of legionella proliferation.

The landlord has asked whether these tanks could be excluded in the assessment as they are residential flats and they do not consider themselves responsible for the necessary monitoring and treatment considering the risk identified?

Q13) 'Fortic' and Other Combination Water Heaters

Would you treat the cisterns on top of "fortic" style heaters and flatbacks the same as main cold roof tanks /cisterns, regarding legionella management?

Assuming that the heater is used on a regular basis and the hot water temperature is correct would they need to be checked for cold water temp yearly (summer) etc. Invariably there is a heat transfer from hot to cold sections and correct temps in the cold tank are difficult to achieve. Is this negated by the pasteurising effect of the heating process?

Q14) Calorifier Vents

Could you tell me where it is written that calorifier open vents must be direct to drain via a tundish?

There is a diagram in ACoP L8 implying this but the Water Regs and the Fittings & Materials Directory have plenty showing the vent going back to the cold-water storage tank.

Q15) Scalding

At what temperature would water scald? The personnel coming into contact with the water are people of working age.

Q16) Direct Mains Supply

Can WMSoc supply a set of guidelines that clearly outline the tests required when having mains drinking water analysis conducted on our premises?

A16) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q17) Temporary Water Supply

Can WMSoc supply a set of guidelines that clearly outline the requirements when having a temporary water supply of drinking water?

A17) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q18) Tanked Water Supply Microbiological Testing

Can WMSoc supply a set of guidelines that clearly outline the tests required when having analysis conducted on drinking water supplied from a tank?

A18) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q19) Water Tanks and Monitoring

What are the requirements for the monitoring of water storage (header) tanks? Where do they come from?

A19) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q20) Tank Cleanliness and Stored Water

I have recently chlorinated a development of a block of brand new apartments, which have boosted water and an 8000ltr break tank.

The developer has called me and explained that the water tank and booster system that has been recently chlorinated will not be put into full use until 3/4 weeks time.

I have explained the tank requires a regeneration of water every 24hrs.

1. While this tank is out of use would it have to be drained down?

2. Would it have to be re-chlorinated?

3. Can it stay filled but with a dose of chlorine added?

4. Can it stay filled and then put into operation in 3/4 weeks time?

A20) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q21) Cold Water Tanks, Storage and L8

We are currently running mains fed cold water tanks serving potable water. If temperatures are not maintained to current guidance as outlined in HSG274 Part 2 what preventative measures do we take? If we are supplying non potable water from a storage tank that is mains fed what maximum temperatures are permissible? If they are not maintained what measure do we take?

A21) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q22) Removal of Cold Water Tanks

Over the last few years we have been taking out most of the cold storage tanks from our schools where reasonably practicable. We are now wondering whether the ClO2 (which was introduced as an interim measure) should continue to be used in those schools where the tanks have been removed.

A22) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q23) Multi-Occupancy Buildings Centralised Hot Water

In a high-rise block of flats with a centralised hot water system, how many hot water taps should be checked and how often? Gaining access to private dwellings is proving difficult, due to being seen as intrusion.

A23) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q24) Bottled Drinking Water

Can WMSoc supply a set of guidelines that clearly outline the tests required when having Bottled drinking water analysis conducted on our premises?

A24) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q25) Private Water Supplies

Can WMSoc please supply a set of guidelines that clearly outline the tests required when having private water supply drinking water analysis conducted on our premises?

A25) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q26) Calorifier Overflowing

I have attended a site where the overflow from the calorifiers are constantly overflowing. The calorifiers used to be direct fired water heaters from gas but have been converted to act as provision for secondary hot water. The opinion of the site is that this problem has been occurring since this change. Would this sound plausible?

A26) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q27) Instantaneous Hot Water Temperatures

Can you tell me, where water is heated instantaneously like from a combination boiler or a point of use (POU) water heater, is it acceptable to have lower hot water temperatures at the outlet? If so what is the lowest temperature acceptable?

A27) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q28) Flexible Hose Replacement Frequency

Do you have any information regarding when newly installed WRAS approved flexible hoses should be replaced in domestic hot & cold water systems (non-healthcare)?

A28) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q29) Removing Non-Approved Flexible Hoses

My approach to flexible braided hoses when carrying out a Legionella Risk Assessment on a domestic hot & cold water system is to recommend that they are replaced with solid pipe work if practicable, failing this, ensure that the hoses are WRAS approved.

If there is no evidence that the existing flexible hoses are WRAS approved (either a tag on the hose or on the nut) I would always assume the possibility that they are not WRAS approved and a remedial action should be carried out.

What are your thoughts on how to identify non WRAS approved flexible hoses and what remedial recommendations would you advise?

A29) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q30) Flexible Hose Use

Can a flexible hose be used to connect a tap to copper for the last 18" / 45cm?

A30) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q31) TMV Inlet Temperature

While going through the standard comments my company includes in our Legionella risk assessments, I noted that our justification for requiring a TMV hot water inlet to be at or above 50°C was derived from L8 Table 3, which is clearly a reference to the 3^rd edition which escaped a previous purge of outdated terminology. Looking to update our comment however, I found no equivalent statement in HSG274 part 2. Has this been dropped as a requirement? If so, why?

A31) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q32) TMV Maximum Mixed Temperatures

I’ve been looking for a definitive answer regarding the allowable/absolute maximum mixed temperature thermostatic mixing valves (TMVs) are allowed to discharge hot water at, particularly in healthcare settings. Is it therefore acceptable to have a TMV mixed temperature control parameter stated as 41°C ±2°C (i.e. 39 to 43°C) for washbasins?

A32) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q33) Maintaining TMTs

Question regarding maintenance of thermostatic mixer taps (TMT). When including TMTs in a cleaning and disinfection regime, would you advise that the integral cartridges are removed from the taps and cleaned? The regime in place at the site I'm currently attending includes C&D of the strainers on hot and cold supply to the taps, but the tap isn't being stripped down and cleaned.

A33) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q34) Flow through expansion vessels

Through Flow expansion vessels for HWS calorifier systems. we have a client who has requested that we look at changing the existing HWS expansion vessels to through flow type, do you have any information on this type of system.

A34) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q35) Flushing Expansion Vessels

Just a quick question as I can’t find any definitive answer on this over recent months as its been brought up a few times.

Expansion vessels- “Where practical, flush through and purge to drain” HSG 274 part 2.

Where do we draw the line? Assuming bacteria could potentially be breeding in an expansion vessel (EV) of any size. Do we ignore 2ltr EVs connected to POUs (as most don’t have drains fitted although could easily be fitted with a combined drain/iso valve) and just include the larger EVs, or recommend any sized vessel be flushed? I appreciate other risk factors involved regarding design/installation.

HSG 274 states ‘where practical’, so some take this as to not flush the smaller vessels, plus these should have increased ‘turnover’/less stagnation, that said, most I check have lost charge anyway or the diaphragm/bladder has ruptured.

A35) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q36) Guidance on Vertical Installation of Expansion Vessels

I have always understood the reason for pressure / expansion vessels to be fitted vertically to prevent silt / sediment etc from forming on the membrane of the bladder within the pressure vessel, i.e. for Legionella control but I can't find any guidance document stating this. Please can you help with guidance and confirmation if I correct or not.

A36) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q37) Minimum Expansion Vessel Volume for Flushing

HSG 274 Part 2 recommends that expansion vessels are flushed routinely (at least six monthly); is there a minimum volume on the expansion vessel to which this guidance should be applied? (e.g. some 5-litre heaters may have 1 litre expansion vessels)
What is the position with regards to “anti-Legionella valves” that promote water flow “through” the expansion vessel?
- Do they negate the need to flush manually?
- Is there a list of approved products?

A37) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q38) Internal Inspection of Cold Water Tanks

With regards to the new British Standard 7592-2022, Sampling for Legionella Bacteria in Water Systems, refers to not removing the lid of a cold water storage (CWS) cistern to prevent any contaminates entering it. This I understand, and makes sense to a degree, so, therefore the question is, are we still allowed to remove lids for internal assessments of CWS cisterns as per HSG274 Part2, or is it up to the discretion of the assessor?

A38) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q39) Bib Tap Flushing

Are bib taps required to be flushed weekly if they are not in use or can they be purged prior to use?

A39) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q40) Checking Return Temperatures

The client at present takes all the TMV outlet temperatures and the flow and return temps at the source i.e. the calorifiers but not at the inlet pipes of the TMVs (due to access for some TMVs). From the response below I gather that these temperatures do not have to be taken as long as the return loops are recorded on a possible quarterly basis.

The HSE’s guidance is that the return legs of circulating hot water systems be checked to confirm that water is flowing throughout the system, as cool hot water can be susceptible to legionella proliferation. The schedule is based on the assumption that there are principal flow and return loops (for example in risers up and down the building) and subordinate loops flowing to and from the principal loops (for example serving facilities on each floor). As there might be a large number of subordinate loops, and once the system is balanced it is likely to remain so, the frequency advocated is quarterly, whilst for principal loops it is as it always has been for noncirculating systems, monthly. If this schedule is followed, deadlegs will be limited to seldom-used and unused draw-off points (which should be identified and flushed or removed as appropriate), making frequent checks on every outlet or feed to TMVs unnecessary. The HSE does, however, advocate checking a representative selection of outlets over time to confirm the temperature throughout. It should be remembered that where there is mixed water rather than hot, use of the cold tap is likely to reduce, so it might become seldom-used or even unused.

A40) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q41) Billy Taps in Unoccupied Buildings

Do you have any specific information on Zip / Billy Taps and the management / monitoring if a building is unoccupied. We have insisted they are still connected and incorporated within the weekly flushing regime but would like to know if you can provide any specific guidance.

A41) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q42) Temperature of Hot Water Storage Vessels

For monitoring the flow temperature from the hot water storage vessel is it acceptable to take the temperature from the nearest hot outlet to ensure that the temperature is over 60^oC?

A42) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q43) Water Heater or Boiler?

Is a 30-50 litre water heater classed as a hot water storage vessel or as boiler. The heater in question is a Zip Aquatpoint 3.

A43) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q44) Taking Shower Temperatures

I have a query on what method should be used for taking shower temperatures? Is it placing a thermapen under the shower head directly or getting a plastic tub and unscrewing the shower head and placing it in the tub, running the water for 1 minute and taking the temperature? I've looked at L8 and 274 and it does not specify a particular way to do this. Is there any Industry standard or best practice I can use as a reference point?

A44) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q45) Multiple Thermostatic Mixing Devices

We have been made aware that a Thermostatic Mixing Valve (TMV) has been installed upstream of a Thermostatic Mixing Tap (TMT).

A45) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q46) Hot Water Storage Temperatures

I'm in a debate with a client in relation to the storage of hot water and what is or isn't the correct procedure.
It clearly states that stored hot water within a Calorifier should be stored at 60°C or higher and should be suitably sized to cope with peak demand. If there is a recirculating system the hot water needs to return to the cylinder no less than 50°C and at 55°C in health care premises.
However, there are a lot of instances where the Calorifier temperature drops below 60°C several times a day, especially at peak demands. As long as the Calorifier temperature does not drop below 50°C and recovers during the day to achieve 60°C or greater and is maintained for a least one hour, in your opinion is this acceptable?

A46) Answers compiled from the experience of the WMSoc technical committee are available to Water Management Society members. To become a member and receive all the benefits of the Water Management Society please click here.

Q1) Care Homes and Dip Slides

Is water testing for legionella or with dipslides necessary or desirable in a care home of the elderly?

Q2) TVC levels

A UKAS accredited laboratory has informed me that there are no definitive limits for TVC levels. However, previous guidance figures of 100 @ 22°C & 20 @ 37°C for ‘water in bottles or containers’ are sometimes offered as a guide. Is this correct? What actions would you recommend be undertaken, on the hot and cold water systems and associated storage vessels, if the test results show levels that exceed the above (e.g. 2400 at 22°C & 3840 at 37°C)?

Q3) Legionella Sampling and Routine Monitoring

I am at present carrying out an audit on various procedures. Many of the procedures I had created over time, but the one relating to the taking of a legionella sample was derived from previous material and I do not know of its original source. I was wondering whether you know of any procedures relating to the optimum method of taking an LP sample. The main contentious area of our current procedure is the timing of the taking of the sample from the water flow. Our procedure refers to running the water flow for 2 mins.

Q4) Legionella Levels

What is the significance of finding Legionella in my domestic water system? I am told the levels detected are considered low.

Q5) Legionella and Risk in Disused Buildings

What is the significance of the risk from Legionella in disused, unoccupied or partially occupied buildings?

Q6) Legionella Monitoring

I currently have a wide cross section of commercial, industrial and local authority clients who contract us to manage their legionella control programmes. We carry out risk assessments, monitor temperatures and follow L8 guidelines as far as possible in managing their control programmes.

We also test for Legionella on a regular basis and would like to firstly reassure our clients that on domestic hot and cold water services a certain percentage of results come back positive. Our policy is to investigate each one to identify the reason behind the result. It would also be a very useful control statistic for ourselves to allow us to assess the effectiveness of our control measures compared to an industry average.

Do you have any figures on the average positive L.pneumophila sero group 1 (or Legionella species in general) as a percentage of samples submitted to laboratories in the UK?

Q7) Using Accredited Labs

Could you please advise if it is statutory when taking water samples in a sheltered accommodation for L.P and TVCs for the Laboratory to be UKAS accredited?

Q8) Mixing Water Samples

I have recently come across several care homes who are being advised by a lab that they can do Legionella Water Sampling by putting water from four different HW outlets into the same bottle. Surely this is poor information, as I am aware that a Lp sample should be from an individual outlet only and not multiple. Also I cannot see any reference in the guidance to the taking of water samples into the same bottle from multiple outlets. I fear these care homes are leaving themselves "wide open" if there were any type of HSE/LA investigation.

Q9) Resampling after Negative Sample Results

I have sampled 11 outlets at a site, two samples (x1 hot & x1 cold, different areas of the building) came back with Legionella pneumophila detected 50 cfu/1000ml. They were both resampled two weeks after the original samples taken which came back clear, nothing detected. Should resampling take place again?

Q1) Mobile Hot Water Hand Wash Stations

One of our customers has purchased several mobile hot water hand wash stations 20Litre. We are currently risk assessing the customers site and our main concern is that the item stores water and distributes it at 42 deg C. Could you provide some thoughts on how to best manage it?

Q2) ESGLI Guidance for Water Systems

What guidance is available for building water systems with regards to COVID-19?

Q3) COVID-19 Reopening of Water Systems

What do you suggest small businesses should do to ensure water is safe before reopening their premises?

Q1) Rainwater Harvesting Systems - Monitoring

My customer is using rainwater systems with filtration and UV treatment on their sites for hand washing and toilet flushing, they are also using 10-litre point of use water heaters. They have been advised by one of the water treatment companies looking after their sites in England that they don't need to check the monthly temperatures of the water due to the nature of the systems on-site and that it only needs to be done once a year? The guidance states monthly but as these are different systems would you agree or disagree with the above recommendation of annual temperature checks as being sufficient or not?

Q2) Metal Working Fluids in Legionella Risk Assessment

We have recently had some conflicting advice over whether water-based metal working fluids should be included within a legionella risk assessment. Under the terms of HSG274 Part 3, we realise that the list of miscellaneous systems is not exhaustive, but the source of this advice came from an HSE Inspector who advised that they felt they need not be included under HSG274. Risk assessment and written scheme

We are aware of the bacterial risk with regards to skin and breathing issues and we have advised in our risk assessments that our clients go to HSE website and adhere to MW3 and MW5, but this is not specifically for legionella risk, but as general health risk.

Q3) Irrigation Tank Monitoring

Is it a requirement that the irrigation tanks for golf courses be risk assessed and monitored the same way as a normal cold water storage tank inside the building feeding outlets or heaters or can they be assessed to a lesser degree due to their usage?

Q4) Temperature Testing of Reverse Osmosis Systems

We would like to understand the maintenance on a Reverse Osmosis system feeding Lab taps.
As legionella is a low risk do you still have to take temperature on outlets?

Q1) Multi-Occupancy Private Residential Flats with Communal Cold Water Tanks

I am the chairman of the Management Committee of a block of privately owned residential flats. The building is made up of three side-by-side blocks, seven stories high. On the roof we have six tank rooms containing water tanks that hold over 2000 litres each, fed from the mains supply. Our Managing Agent has told me that because we are the representatives of the Owner and we are supplying water to each of the 55 flats within the blocks, legislation demands that we have a Legionella risk assessment programme. Mains water is also fed directly to each flat.

We have had a survey and risk analysis done, but the company who carried it out are suggesting that we should include temperature checks on all water taps within all the flats every six months. We believe that this far exceeds our responsibility and is largely motivated by commercial factors.

I would greatly appreciate some guidance on what we are obliged to do, bearing in mind that we are only responsible for the supply of cold water to residents.

Q2) Council/Housing Associations & Legionella Risk Assessment

Should all properties under the control of Council Housing Associations (2500 domestic dwellings in one case) have a legionella risk assessment carried out?

Also what monitoring regime should be initiated (if any) for the water systems within these properties?

There is a mixture of multi occupancy flats with communal storage tanks and calorifiers, individual houses with their own tanks and calorifiers, and flats/houses with mains fed cold water services.

Q3) Risk Assessment

Is there a set format for conducting a Risk Assessment annual review/update as applied to buildings, i.e. what procedure is required to conform with ACOP L8 (Fourth edition) Published 2013 as far as documentation is required?

Are we required to take water temperatures and bacteria tests etc?

We understand the requirement to report on changes to the building and system, but how far do we go with the already assessed systems without creating a completely new risk assessment?

Q4) Risk Assessment of Outside Taps etc.

We have had our main buildings risk assessed for legionella but I am not sure if such items as outside taps, standpipes in our parks and gardens, isolated sinks in stores which have mains fed hot water heater, etc need to be risk assessed.

Q5) Legionella Risk

At what levels does legionella become a problem to human health?

Q6) Audits

How often should audits be carried out?

The LCA state that a review should be undertaken at least annually, and in L8 there is no reference to review frequency (apart from risk assessment frequency). Is there any necessity or requirement to audit/review on a set frequency or is it annually unless there is a reason to review more frequently if higher risk or problems found?

Q7) Negligible Risk

How can we decide what level of risk is negligible; this is the detail I am struggling hard to ascertain?

Being self-employed surveyor looking at my PI cover has made me question things in great detail but in this case the possibility of infection is my prime motive. Would a consultant advise upon level of risk for occasionally used sinks etc. and if so, how would he do it?

Q8) The Written Scheme

Please can you advise of whom, in your opinion, should write the written scheme?

Q9) Temperature Recording in Risk Assessment

I've been recently asked by somebody I work with if it is mandatory to record all the temperatures in the Legionella Risk Assessment report. It has been suggested to me that as long as all the temperatures that fail are recorded, this could be deemed as acceptable. Can you please point me in the right direction as I've heard different opinions?

Q10) WRAS Approved Fittings Use

I have been asked to supply a written scheme to place in my legionella water management log book about the importance of using WRAS approved fittings on hot and cold water systems (to prevent bacteria growth) is this something you could help me with? I have been in touch with WRAS but didn't get very far.

Q11) Risk Assessment of New Installations

Could I please have some clarification on the following and where I would find the relevant clauses in ACOP L8: “Is there a requirement to carry out a risk assessment on a brand new, consultant lead plumbing installation...I am under the impression that there is a requirement to carry out RA but my client thinks otherwise”

Q12) Risk Assessing Evaporative Air Cooler Systems

Evaporative Air Cooler systems such as cool breeze systems, how should these be considered in a Legionella Risk Assessment and what controls should be in place?

Q13) Recommending Temperature Monitoring for Biocide Controlled Systems?

If a client has a system that is primary controlled by biocide (chlorine dioxide), should they also be taking temperatures and keep record of these? From a risk assessment point of view, should we be recommending temperature monitoring?

Q14) Temperature Monitoring Low Risk Systems

I have been asked to quote for a tender involving a lot of properties that have mains water to a kitchen sink, WC, wash hand basin, and a water heater under 15 litres. They presently carry out monthly temperature monitoring at these sites.
In HSG 274 Part two, info box 2.2, it talks about low risk systems. Would I be right in saying that a low risk system, as described in info box 2.2, does not require monthly temperature monitoring, and would probably just require an annual inspection? I believe the above to be the case.

Q15) Need for Risk Assessment of Single Occupancy Buildings

A client has vaguely alluded to a HSE legal form or document that can be filled in stating that a building does not require an LRA. Either in the case of a building having no communal or landlord responsibility services or in the case of a single occupancy demise with all systems falling onto the tenant to manage.

It was my understanding that an assessor must attend site anyway and produce an assessment even in brief that confirms this fact and acknowledges it formally.

Would a brief site survey document suffice that has been carried out internally?

Q1) The Responsible Person

When looking to draw up a management structure recently the following question arose. Where a Council has delegated the management of its Housing stock to an ALMO Organisation, who becomes the responsible person the Council or the Almo (outsourced facilities management company), and if it is the Council is there a need for a named individual to take ultimate responsibility?

Q2) Using Contractors as the Responsible Person

For the client/employer/controller of workplace premises to use a contractor as the ‘Responsible Person’ under L8, what authority and power would the client have to allocate to the contractor in order they can actually fulfil their duties?

Q3) Retirement Development

The interpretation and application of the ACOP L8 in retired development and private dwellings is becoming something of a trial to all concerned and I would appreciate clear guidelines.

We live in a retirement development of 38 flats. Each living is independent of the other. Each flat with its own tank and water supply, and each heating their water supply as required; what are the guidelines for a monitoring regime for the water systems within these properties?

Q4) Labelling of Pipework

Please can you provide details-regulations on the correct labelling of pipes (hot water, cold water, storage tanks, non-drinking water and drinking water etc.) on the following premises?

Nursing homes
Residential homes
Care homes
Sports facilities
Offices
Hotels

Q5) Regulations and Guidance

What are the relevant Regulations and Guidance for Residential Care Homes?

Q6) Responsibilities

Could you please let me know who is responsible for the legionella testing and health & safety in a building, which consists of individual flats and common areas? (The flats are supplied from a common main, but each flat pays rent that includes the water supply. They also pay their own electricity. This includes water heating).

Q7) The Irish L8

Is there an equivalent to L8 in use in Ireland?

Q8) Pipework Labelling

Please can you provide details-regulations on the correct labelling of pipework

e.g. for Hot water, cold water, storage tanks, non-drinking water and drinking water etc.

Q9) Does Shower Head Replacement Meet HSG274 Requirements?

Some of our customers are being offered a product which alters the control regime. The product is a shower head and hose which contains an insert for spray production. The USP is that this insert is switched out quarterly, removing the need, or so claimed, for traditional descaling and disinfecting. Each shower has four different colours of insert, denoting which quarterly period they are in.

Our concern as a water hygiene monitoring provider, is where this stands on a compliance perspective. If we no longer clean and disinfect the units, but instead help the customer change out the coloured inserts, are we fulfilling our obligations under HSG-274?

Q10) Infra-red Thermometers

I have seen a water company technician using an infra-red thermometer for taking outlet temperatures. There appear to be contradictory opinions such as water is the ideal medium as most detectors are calibrated using ice water at 0 centigrade . This is then contradicted elsewhere commenting that reflection from the water will give inaccurate readings. This is further contradicted by the comment that reflection is not an issue as the detector does not emit but only receives infra-red radiation.

Can you advise me please?

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