All water fittings in the UK, including water tanks, must comply with the Water Supply (Water Fittings) Regulations and, in Scotland, the Scottish Water Byelaws. There are various bodies that provide guidance on these requirements, such as WRAS and the HSE.

In WRAS’ own words, the purpose of this regulatory regime is “protecting public health, safeguarding water supplies and promoting the efficient use of water within customers’ premises across the UK”.

In practical terms, it means that all water fittings should follow appropriate harmonised conditions set out by European or UK guidance. The easiest way to check this is to look for fittings that bear a CE marking and are included in the “Water Fittings and Material Directory” produced by WRAS.

There is detailed guidance provided by the BSI for the specific water tank being installed and any procedures that are involved. The table below demonstrates where this advice can be found:

The prevention of backflow is a fundamental requirement in the regulations and byelaws. Backflow occurs when water travels in the opposite direction to the one originally intended, and back towards the mains supply or water tank. This is dangerous as the water can come into contact with bacteria and other contaminants, and therefore present a health risk to users of the water supply. To prevent backflow, every water tank must be fitted with:

• An overflow pipe that provides warning of an impending overflow;
• A cover that is not watertight but stops light, dust, insects and animals from getting into the tank;
• Thermal insulation to minimise the risk of freezing or undue warming.

In a nutshell, the water tank must be installed in such a way that it minimises risk of contamination. It should also be of a suitable size, and any pipework must allow water to move freely away from the tank so there is no possibility of stagnation.

The HSE’s legionella guidance makes reference to The Water Supply (Water Fittings) Regulations and Scottish Water Byelaws, and maintains that installation of water tanks must strive to meet their requirements.

It also recommends checking that the materials used within the water tank are compatible with the characteristics of the water supplied to the building, minimising the risk of corrosion, and will not support the growth of bacteria like legionella (ruling out natural rubber and hemp, for example.)

Finally, the guidance also states that water tanks should be easy to access by engineers for management and maintenance purposes.

Want to check if you comply with the HSE’s guidance? We’ve put together a checklist that allows you to quickly see if you’re compliant with the health and safety regulator’s legionella control and prevention guidelines.