The Water Management Society


Here at Concept we’re proud of the depth of knowledge of our team members. Here’s Ben Gibson congratulating Nigel Tooth on his article for Waterline Journal earlier this year.

Extract from Waterline – the magazine of The Water Management Society

Legionella Control within Hot and Cold Water Systems in a Time of Covid
by Nigel Tooth – Associate Director Spring 2022

March 2020, we all remember how it felt in those early days of the Covid-19 pandemic. It was our John F Kennedy moment or was maybe reminiscent of where we were when we first heard the news of John Lennon’s assassination. All nonessential high street businesses were closed to slow the spread of infection, with people instructed to stay at home other than for essential purposes only. We can all recall the rush of people to shut up shop before racing back to the sanctuary of home. Cities suddenly became ghost towns. The London underground which had previously been standing room only with insufficient space to open a newspaper, in an instant the new normal was to have an entire carriage to oneself. To date passenger levels have yet to return to what was once considered every day. The streets of London became like a set for the movie 28 Days Later.

Despite lockdown measures organisations remained bound by health and safety legislation, including the Health and Safety at Work Act 1974 and The Control of Substances Hazardous to Health 2002. The Health and Safety at Work act continued to apply. It remained necessary to have in place a suitable and sufficient risk assessment document for duty holders to identify and assess the risk of exposure to the legionella bacteria from work activities and water systems. The government offered no advice on relaxing statutory obligations and so compliance to statutory guidance contained within the ACOP L8 still needed to be maintained. Under these pieces of legislation organisations must have legionella risk assessments and must implement control measures to reduce the risk as far as is reasonably practical (HSWA, 1974; COSHH, 2002). It further remained necessary to have in place any precautionary measures to enable adequate management of risks.

The effects of the lockdown including building closures with drastically reduced occupancy, also created difficulties for external contractors when attempting to visit sites for essential maintenance purposes. Such factors dramatically reduced water turnover resulting in lapses of control measures, thus drastically increasing the risk of building water systems becoming subject to microbiological infestation, including from the legionella bacteria. Under the British Standard guidance on legionella risk assessment, (BS 8580-1:2019; 10.1), such changes warranted a review of site risk assessments. This meant that for premises taking lockdown measures, any pre lockdown risk assessment was unlikely to still be suitable for such radically altered conditions.

Responsible water hygiene providers provided practical advice bulletins based upon industry standard guidance, detailing actions intended to ensure that premises remained safe for occupants. Some water hygiene companies were granted status as essential workers to enable them to continue operating as normal in carrying out flushing of little used outlets along with validation sampling. Water hygiene providers operating in line with the government’s hygiene and social distancing guidelines ensured that all operatives were equipped with suitable PPE and were carrying out risk assessments on a site-by-site basis to reduce risk to both themselves and to members of the public. Such actions were intended to ensure the safety of buildings during periods of heavily reduced occupancy to keep water services online and safe. Significantly reduced occupancy poses a particularly high risk within larger buildings with increased stored water capacities. The aim was to maintain control measures and for water system turnover to mimic normal occupancy.

For buildings where it was decided to maintain water systems, the two most effective legionella control measures for domestic water systems were by maintaining of compliant hot and cold water temperatures and by ensuring sufficient turnover throughout the system by means of a robust flushing regime (HSG274: Part 2; 2.32; 2.36; 2.78). For such control measures to be effective they must be carried out correctly by competent persons (HSG274: Part 2; 16) which could be achieved by using either water hygiene engineers or by suitably trained members of staff. A further option for temperature monitoring is by using remote technology involving a network of temperature sensors installed in key parts of the building’s water system to provide real time temperature monitoring data. The advantages of such an approach would be as follows:

• Temperature monitoring compliance can be ensured without monthly visits from an engineer after the devices are initially installed

• Provision of regular reports detailing temperature compliance and where flushing should be carried out in response to non-compliant temperatures

Concept Environmental Solutions were heavily involved in carrying out regular flushing programmes, particularly within major educational establishments, with the aim of mimicking normal building water usage. Such actions were put in place to limit the negative impacts of systems being disused and to minimise the costs of recommissioning buildings upon resumption of normal operation (HSG274: Part 2; 2.50). Advice to clients included the following;

• Routine Water Hygiene Tasks: It is of critical importance that normal building water usage be replicated. It is therefore necessary to ensure that a robust water hygiene maintenance programme be maintained, including regular flushing of low-use outlets, temperature monitoring, thermostatic mixing valve inspections along with showerhead cleaning and descaling etc. If there are lapses in control measures, then samples should be obtained for legionella analysis by a UKAS accredited laboratory to ensure that the building water system has not become colonised with legionella (HSG274: Part 2;
2.122). Legionella samples should also be taken 10 to 14 days prior to building services resuming normal operation

• CWS Tanks: Cold Water Storage Tanks should be sized to ensure that water usage is sufficient that stored water is not stagnating (HSG274: Part 2; 2.58). This means that a complete turnover of water should be achieved within a 24-hour period. In the case of split section CWS Tanks it may be possible to isolate a section to reduce stored water volume, although the manufacturers should first be consulted. It may therefore be advised to reduce the stored water content within both sections by lowering ballvalves or installation of drop-arm ballvalves. If it is felt necessary to fully drain CWS Tanks, then they will need to be inspected, refilled, and disinfected with potable water samples obtained for analysis by a UKAS accredited laboratory

• HWS Generators: Whether smaller point of use HWS Heaters or larger HWS Calorifiers, it is important that they are not turned off as the maintained heat will inhibit the colonisation of the legionella bacteria. It is necessary to ensure HWS Generators continue to operate at compliant temperatures of 60°C on the flow and not less than 50°C on the return, along with not less than 55°C in healthcare premises. If HWS Heaters have been turned off for more than a week, then they should be disinfected prior to being taken back into service (HSG274: Part 2; 2.127)

• Little Used Outlets: A little used outlet is classified as an outlet used less than once per week. This includes not only taps but showers, washing machines, vending machines and bib taps as a few examples. A competent person needs to review the building water system to identify any little used outlets to ensure that each one is thoroughly flushed at least once a week. This should be achieved by reviewing the low use outlet register within the site logbook and adding new areas that have become infrequently used. This activity must be recorded and reviewed by the sites responsible or deputy responsible person on a regular basis. The idea of little used outlet flushing is to mimic normal building water system occupancy to reduce the risk of microbiological proliferation, including from the legionella bacteria.

This should always be a major factor when considering the extent and frequency of little used outlet flushing to be carried out. It is also necessary to take great care to minimise the generation of aerosol when carrying out low occupancy flushing as this is how the legionella bacteria is transmitted. To minimise risk of flooding, it is further recommended that outlets should not be left unattended during flushing procedures.

For buildings where it was decided to decommission water systems, the following course of action was recommended;

• CWS Tanks: These should ideally be drained and allowed to dry to prevent the formation of biofilm or stagnation that would encourage the proliferation of microbiological infestation, and to minimise the risk of a possible flooding. It is however important to bear in mind the possibility of leakages that could be caused by contraction and expansion when draining and refilling sectional GRP CWS Tanks

• HWS Generators: Such units, whether smaller point of use HWS Heaters or larger HWS Calorifiers should wherever possible not be turned off, as hot water will inhibit the colonisation of bacteria including legionella. Continue to ensure HWS Generators are operating at compliant temperatures of 60°C on the flow and not less than 50°C on the return, along with not less than 55°C in healthcare premises

• Hot and Cold Water Pipework: Do not drain pipework as this can promote the growth of biofilm including pseudomonas (HSG274: Part 2; 2.52) along with creating conditions suitable for corrosion damage

• Signage: Ensure that clear and visible signage is placed throughout the building to state that the water system has been decommissioned and is not safe to be used

Some companies and organisations adhered to the requirements. Others, such as within catering and entertainment sectors already reeling from the financial implications of lockdown, felt unable to take further financial hits to already ailing businesses. In pure cost terms it can be argued that the cost of the pandemic has already outstripped the financial cost of the second world war. An updated statement on Covid19 from the Legionella Control Association however noted There is potential for multiple outbreaks of Legionnaires’ disease following the COVID-19 outbreak if actions taken now are not carefully considered. Public Health England (PHE) guidance stated that there should be regular flushing of the water system at the likes of dental practices, hairdressers, gyms, and hotels, as well as office buildings, to stop bacterial growth.

At long last in May 2021, the lockdown finally appeared to be easing. At this point responsible water hygiene providers recommended that considering the clearly longer-term closure due to the COVID-19 pandemic than had been originally envisaged, that hot and cold water systems be properly recommissioned to SFG 30 standards (Guide to good practice-mothballing and recommissioning of buildings) following mothballing. This was intended to ensure the safety of system users prior to water services being returned into normal operation.

For smaller MCW only systems serving for example a couple of wash hand basins, toilet pans plus a kitchen sink as may be found within staff retail premises, it could on occasions be sufficient to carry out copious flushing of outlets followed by obtaining of samples from a representative number of hot and cold water outlet points for analysis by a UKAS accredited laboratory for Total Viable Counts, Coliforms, E.Coli and Legionella.

For larger systems involving hot and cold water storage facilities, a start-up approach as follows was recommended in accordance with the ACOP L8 and BS8558 to ensure that the systems were safe to operate;

1) Refill any CWS Tanks that have been drained during the lockdown period, check for any potential leaks that may have occurred due to contraction and expansion

2) The entire hot and cold water system should be thoroughly flushed, ensuring there is complete turnover of system water capacity (HSG274: Part 2; 2.127)

3) It is of critical importance to minimise the generation of aerosol, as this is how the legionella bacteria can be transmitted, for items such as showerheads it may be necessary to run water through plastic bags to prevent the creation of aerosols

4) Do not leave flushing of outlets unattended, the potential for basins and sinks etc to overflow and cause a flood is a real risk

5) A complete system disinfection with chlorine to be proportionally injected via the incoming mains cold water supply to a concentration of 50mg/l. Chlorine should be drawn through every outlet and water storage vessel, testing concentrations throughout the building, and ensuring a contact time of at least one hour

6) Following completion of disinfection, validation samples to be obtained for analysis by a UKAS accredited laboratory for Total Viable Counts, Coliforms, E.Coli and Legionella at representative outlet points throughout the system (HSG274: Part 2; 2.120)

7) Inspect CWS Tanks for potential leakages and for compliance with current standards and byelaws. Should they supply drinking water then a potable sample should be obtained for analysis by a UKAS accredited laboratory to ensure that they are fit for purpose

8) Ensure that any overdue water hygiene tasks, including temperature monitoring, HWS Calorifier inspections, microbiological samples, thermostatic mixing valve inspections plus showerhead and spray-tap descaling etc are completed prior to the building being reoccupied

So where do we go from here, and will there be a need to strengthen existing guidelines covering water hygiene? Below are some considerations:

• Hospitals and Care Premises: As a responsible water treatment company, we have noticed an increase in legionella positive results from water samples within the care sector. The likelihood must be that with so much focus being placed upon prevention of Covid, that routine water hygiene tasks such as regular flushing of little used outlets and temperature testing of hot and cold water outlets is not always being carried out as stringently as is necessary. It may therefore be prudent to adopt an automated approach to such regular tasks

• Is this the New Normal? Back in March 2020 the consensus seemed to be that the pandemic could potentially all be over within a few months. Yet here we are some two years later faced with a second variant, spreading like wildfire, and threatening to overwhelm the NHS. Until the entire world is vaccinated there must be the risk of more and potentially more deadly variants. Faced with such an uncertain future, how long will it take for water systems within office and retail premises to be subjected to the type of normal water consumption necessary to avoid stagnation which will encourage microbiological proliferation

• Homeworking: In the initial rush of people to shut up shop before racing back to the sanctuary of home, companies were desperate for employees to set up home offices and to carry on working as best as they could. Many of those employees however found that they didn’t miss the daily commute, that they rather liked this facet of the new normal. Faced with such an uncertain future, will water systems within office and retail premises ever again be subjected to the type of water consumption necessary to avoid stagnation which will encourage microbiological proliferation?