Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Back flow protection
  • Title : Backflow protection for storage cisterns water storing wholesome water
  • Clause Reference : Schedule 2 paragraph 15 (4) (b)
  • Reference Number : B42
  • Decision Date : May 2010

Having been discharged into a storage cistern, water can no longer be considered as water supplied directly from the water undertaker’s main and backflow protection must be provided at the inlet to the storage cistern. Whilst it is the custom and practice is to install a type AG air gap at the inlet, alternative suitable backflow protection such as a single check valve is equally acceptable.

Note: A means of warning for an impending overflow and an overflow are still required (see I16).