Water Supply Industry Interpretations and Advice
- Area of Interest : Backflow Prevention
- Topic : Fluid category
- Title : WCs
- Clause Reference : Regulation 4 & Schedule 2 paragraph 15
- Reference Number : B58
- Decision Date : March 2014
Although a Type AUK1 air gap must incorporate a Type AG air gap the Regulators’ Specification (test code sheet 2212.3 Annex B) permits the installation of an alternative fluid category 3 backflow prevention arrangement for WC flushing cisterns only.
In recognition of this, where an inlet feeding a WC flushing cistern fails to meet the requirements for a Type AG air gap (please refer to interpretation E04) water suppliers may be willing to accept an alternative fluid category 3 backflow prevention device in place of a Type AG air gap. This will however be dependent upon a risk assessment of the WC. Factors that will be taken into consideration will include, but are not restricted to whether:-
- the cistern incorporates an outlet control which ensures the pipework connecting the pan and cistern is completely evacuated between flushes; and
- if there is any risk of back pressure.
[Also see interpretation E03]