Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Temporary filling loops
  • Title : Disconnection of temporary filling loops
  • Clause Reference : Schedule 2 paragraph 24 & G 24.2 (a)
  • Reference Number : B54
  • Decision Date : June 2012 (revised July 2018)

Where a closed circuit (heating system etc) has been categorised by the water undertaker as a fluid category 3 risk the installation of a compliant double check valve on the fill point connection to the supply/distribution pipe may be considered as acceptable backflow protection.

Where a fill point connection incorporates a “flexible connection”,when not in use it is good practice for the hoses on these connections to be completely disconnected and removed, however a partial disconnection, that is to say only detaching one end of the hose, is equally acceptable providing that the disconnection is made between the hose and the backflow prevention device on the supply/distribution pipe.

Please note:if the water undertaker has concerns about the likelihood of contamination, or the suitability of a double check valve - for example due either to age, operating temperature or pressure fluctuations – under schedule 2 paragraph 15(4) they can require the installation of additional backflow protection.


(Also see B22 'Filling and topping up heating system primary circuits')