Water quality testing can be useful in determining the existing physical, chemical and biological characteristics of the water system. Normally, water quality testing is performed when there is a concern about the taste, odour or appearance of the water or where someone has fallen ill and is concerned that the water may be to blame. Water quality testing may also form part of the routine monitoring of the system, particularly where the source is a private water supply or where the system uses chemical biocide control.
Water systems in both commercial and residential premises are susceptible to the risk caused by Legionella bacteria. Negligence on the part of the building owner may result in an outbreak of legionnaire’s disease so employers are bound by law to carry out water quality monitoring and make sure that the water system is safe to use. The question is often raised as to whether Water quality testing should include sampling and analysis for legionella and other general bacteria.
The Health and Safety Executive (HSE) has detailed guidelines concerning quality testing of water as documented in the approved code of practice ACOP L8. It is more of a priority to identify the conditions that could allow legionella bacteria to grow and to eliminate or control such conditions than to sample the water to determine if legionella bacteria are present or not (which is not a control measure).
There are instances where sampling and analysis would be relevant such as following an outbreak of Legionnaires ’ disease, where control measures have not been consistently achieved or where chemical biocides are used as an alternative to water temperature control.
The sampling should be carried out by a trained individual using approved methods and the analysis should be completed by an accredited laboratory with the findings interpreted and reported with any subsequent recommendations.
More important than water quality testing is water temperature monitoring – completed every month – as this allows the building operator to identify any areas where temperatures are non-compliant or within the range that would support the growth of legionella.
The temperature of hot water should be more than 50°C and cold water should be less than 20°C at the sentinel outlets (nearest and furthest taps from the stored water source). Temperatures falling outside of the recommended range should be investigated and remedial action taken to ensure that the water system is quickly restored to compliance.
Cold water storage tanks should also be storing water below 20°C and the flow temperature from a hot water calorifier should be a minimum 60°C to ensure that the water reaches the sentinel outlets within the required parameters.
In the event of an outbreak, it is often found that employers or property managers have neglected the routine water temperature monitoring and therefore been oblivious to the increased risk. It is important to ensure that a health and safety consultants regime is established and maintained if the risks from legionella are to be managed on a long term basis.