Domestic hot and cold-water services
HSG274: Part 2 states where necessary, hot and cold water services should be cleaned, flushed and disinfected in a variety of situations such as; on completion of a new water installation or new components; where the water services have not been flushed as recommended by the control measures; on routine inspection of the water tanks; following water sample results that indicate evidence of microbial contamination of the water system; during an outbreak of legionellosis that is linked to the system; or where indicated by the risk assessment.
All domestic clean and disinfection works are carried out in line with PD855468.
Potable water systems
BS 8558 (the complementary guidance to BS EN 806) states tanks storing drinking water should be inspected annually or more frequently if fouling is suspected. Cleaning and disinfection should take place annually or sooner if monitoring indicates deterioration in aesthetic or microbiological quality. These systems are usually found in large apartment blocks or student accommodation where the communal water tanks supply drinking water.
The clean and disinfection is normally part of package which includes six-monthly microbiological sampling and an annual tank inspection.
Evaporative cooling systems
Legionella bacteria are more likely to proliferate in water systems that are fouled with deposits and biofilm that can protect the organisms from water treatment and provide nutrients for them to multiply. There is an increased risk of this within an evaporative cooling system, therefore it is important to maintain cleanliness.
HSG274: Part 1 states that an evaporative cooling system should be cleaned whenever it is known or suspected to have become fouled (this is normally identified on inspection). However, as cleaning operations are disruptive, it is common to adopt a precautionary approach, with cleaning operations being scheduled to coincide with planned shut-downs, for e.g., every six-months.
All clean and disinfection methods used are in line with the procedure set out in HSG 274: Part 1.
On completion of any clean and disinfection C&S Water Treatment Ltd will issue a clean and disinfection certificate and photographic evidence will be provided if required.