Water Supply (Water Quality) Regulations 2016 — Pure Water Systems, Tank Cleaning and Water Quality Compliance

The Water Supply (Water Quality) Regulations 2016 set the legal standards for drinking water quality in England. They are enforced by the Drinking Water Inspectorate (DWI) and implement the EU Drinking Water Directive in English law. For industrial cleaning operations, the Regulations are relevant in two specific contexts -- the use of pure water (deionised or reverse osmosis water) systems for window cleaning and solar panel cleaning, and the cleaning of water storage tanks and distribution systems that form part of the drinking water supply chain. Operators who contaminate the water supply through inadequate cleaning practices or inappropriate equipment connections face serious regulatory and liability consequences.

Pure water cleaning systems -- the water quality context

Pure water cleaning systems -- used for window cleaning, solar panel cleaning and external building cleaning -- use deionised or reverse osmosis water that has had minerals and dissolved solids removed. Pure water leaves no mineral deposits as it dries, enabling streak-free cleaning without detergents. The water quality requirement for effective pure water cleaning is typically below 10 parts per million (ppm) total dissolved solids (TDS), measured by a TDS meter.

The Water Supply (Water Quality) Regulations are relevant to pure water operators because the deionisation or reverse osmosis process produces a reject water stream -- water with elevated dissolved solids -- that must be managed as waste water and discharged appropriately. Reject water from RO systems is not potable and must not re-enter the water supply. Where reject water contains elevated mineral concentrations it may also require management under environmental permitting requirements. See: Environmental Permitting guidance

Solar panel cleaning -- equipment and compliance | Solar panel cleaning guide

Water supply tank cleaning -- the regulatory context

Cold water storage tanks that form part of a building water supply system are subject to water quality requirements under the Water Supply (Water Fittings) Regulations 1999, the Water Supply (Water Quality) Regulations 2016 and the Water Industry Act 1991. Physical cleaning of cold water tanks is a core Legionella control activity under HSE ACoP L8. The cleaning and disinfection process must not introduce contaminants into the water supply. Equipment used for tank cleaning must be clean, decontaminated and free from contamination before entry into a potable water tank.

Cleaning chemicals used in potable water tanks must be food-grade and approved for use in contact with potable water systems -- not standard industrial cleaning chemicals. The Water Regulations Advisory Scheme (WRAS) publishes a list of approved products for use in water supply systems. See: Legionella control and ACoP L8

Backflow prevention -- Water Supply (Water Fittings) Regulations 1999

The Water Supply (Water Fittings) Regulations 1999 prohibit backflow of contaminated water into the public water supply from connected equipment. Pressure washers connected to the mains water supply must have an appropriate backflow prevention device fitted. The correct backflow prevention device depends on the fluid category of the risk -- a pressure washer connected to a chemical injection system presents a higher backflow risk than a machine drawing clean water only. See: Water Supply (Water Fittings) Regulations 1999