Cold water storage tanks are one of the most common sources of water quality and Legionella problems in commercial and residential buildings. Keeping them compliant is not optional: several overlapping regulations and standards set out how they must be designed, maintained and protected. This guide explains the key cold water storage tank regulations in the UK and what compliance looks like in practice.
Which regulations and standards apply?
- Water Supply (Water Fittings) Regulations 1999 – the core legal requirements for preventing contamination, waste and backflow in water fittings, including storage tanks.
- ACOP L8 and HSG274 Part 2 – the Health and Safety Executive’s Legionella guidance, which covers how stored water must be controlled to prevent bacterial growth.
- BS EN 806 and BS 8558 – British Standards for the design, installation and maintenance of water systems inside buildings.
Together these mean a cold water storage tank must be built from the right materials, protected from contamination, kept cool, and inspected and maintained on a regular basis.
Key requirements for a compliant tank
A close-fitting, protected lid
Every tank must have a rigid, close-fitting lid to keep out light, dust, insects and vermin. Overflows, warning pipes and vents must be screened to prevent anything entering the stored water.
Insulation and temperature control
Stored cold water must be kept below 20°C, the temperature above which Legionella bacteria multiply more readily. Tanks should be insulated and kept away from heat sources to maintain this.
Approved materials
Tanks and fittings must be made from suitable, approved (WRAS-listed) materials that will not taint the water or support bacterial growth.
Correct sizing
A tank that is too large for demand leads to stored water sitting and stagnating. Tanks should be sized so that water turns over regularly.
Safe access for inspection
Tanks must be positioned so they can be safely accessed for inspection and cleaning.
How often must a cold water storage tank be inspected and cleaned?
HSG274 recommends inspecting cold water storage tanks at least annually as part of Legionella control. The tank should be cleaned and disinfected whenever an inspection shows it is necessary, for example when there is sediment, debris, corrosion, biofilm or signs of contamination. There is no fixed cleaning interval; the inspection determines the need.
Common compliance failures
- Missing, damaged or ill-fitting lids
- Unscreened overflows and vents letting in insects or debris
- Stored water above 20°C due to poor insulation or heat gain
- Oversized tanks causing stagnation
- No record of inspections or cleaning
- Corroded or failing tanks that need replacement
Frequently asked questions
What temperature should a cold water storage tank be?
Stored cold water should be kept below 20°C to limit Legionella growth. Insulation and sensible tank positioning help maintain this.
How often should a cold water tank be cleaned?
There is no fixed interval. Tanks should be inspected at least annually and cleaned and disinfected whenever the inspection shows it is needed.
Do domestic properties need to follow these regulations?
The Water Fittings Regulations apply to domestic and commercial systems alike, though larger and higher-occupancy buildings carry greater Legionella duties under ACOP L8.
Keep your cold water storage tank compliant
London Water Treatment provides cold water storage tank inspection, cleaning, disinfection and replacement across London, helping you meet your legal duties and keep stored water safe. Call 020 4532 7773 or get in touch for advice or a quote.