Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Fire sprinklers
  • Title : Fire sprinkler systems - backflow protection 
  • Clause Reference : Regulation 3 Schedule 2 paragraph 15 
  • Reference Number : B18
  • Decision Date : February 2002 (Revised October 2011 & August 2019)

The following information relates solely to fire sprinkler systems, connected directly or indirectly to the mains water supply.

Mains fed fire sprinkler systems without additives are classed as a fluid category 2 risk and a backflow prevention device or arrangement rated to at least fluid category 2 must be installed on the branch feeding the fire sprinkler system.

Mains fed fire sprinkler systems using additives (e.g.rust inhibitors) are classified as a fluid category 4 risk and a backflow protection device or arrangement rated to at least fluid category 4 must be installed on the branch feeding the fire sprinkler system.

Where fire sprinkler supplies are taken from a supply or distributing pipe conveying water to be used for domestic purposes (i.e.water used for drinking, bathing, cooking or washing.) the backflow prevention arrangement should be installed on the fire sprinkler pipework as close as is reasonably practicable to the point of connection to the supply or distributing pipe. 

Dedicated storage cisterns supplying fire sprinkler systems are classed as a fluid category 5 risk and appropriate backflow protection shall be required. The pipework supplying the storage cistern may still be classed as a fluid category 2 risk and be protected as above.