As part of an adequate water management plan, identified expansion vessels will require routine flushing to remove any possible water stagnation within the vessel and associated pipe work. Expansion vessels have been shown to increase the risks associated with bacteria growth because when a pressurised system is running efficiently, there could be long periods without flowing water.

Stagnation in water systems provides an optimal environment for bacteria to grow. Expansion vessels have been shown to increase the risks associated with bacteria growth because of their seldom usage and materials of construction.

The HSE have therefore released several recommendations to minimise this risk.

• Expansion vessels should be located in cool places on cold pipes, close to the incoming mains water supply.
• Expansion vessels should be mounted vertically to reduce debris becoming trapped.
• They should be fitted with a flush through valve and isolation valve.
• Finally, vessels should be designed to reduce the water held inside and stimulate the flow