Water Supply Industry Interpretations and Advice
- Area of Interest : Backflow prevention
- Topic : Fluid category
- Title : Humidifiers
- Clause Reference : Schedule 2 paragraph 15 & G15.3
- Reference Number : B40
- Decision Date : May 2010
Those Humidifiers which introduce water either as steam or by spraying it into an air stream are regarded as a fluid category 2 risk. Where these units are supplied with a drain to waste a fluid category five device such as an air break to drain is required at the waste connection.
Humidifiers that pre-treat water using reverse osmosis units that employ larger scale industrial processes which use chemical additives, for example to clean the reverse osmosis membrane are, depending upon the outcome of a risk assessment, either a fluid category 4 or 5 risk.