Water Supply Industry Interpretations and Advice

  • Area of Interest : Backflow prevention
  • Topic : Flexible hoses
  • Title : Restraining rings for backflow protection of flexible shower hoses
  • Clause Reference : Schedule 2 paragraph 15 & G15.3
  • Reference Number : B20
  • Decision Date : June 2002 (Revised June 2011)

Constraining the outlet of a flexible shower hose, so preventing it from being placed below the spillover level of the shower tray or bath, or reaching the WC, by means of a retaining ring is an acceptable means of backflow prevention.

Robust factory applied retaining rings of the design which do not allow the shower hose to be removed are a recognised method of maintaining an AUK3 air gap acceptable in all types of premises.

Below is an example of a non-removable retaining ring - which is designed so that the hose cannot be removed or detached from the retaining ring acceptable in all premises.

Other types of retaining ring are not acceptable in high risk premises and will only be acceptable in domestic premises if a risk assessment indicates that the highest level of risk to which it would be exposed would be fluid category 3.

Below are three examples of retaining rings which are NOT acceptable in high risk premises because the hose can be removed from the retaining ring


For further information please refer to WRAS information note ‘Prevention of the risk of backflow in the design of domestic bathrooms’.