The Byelaws classify backflow risks according to the severity of the potential contaminants – using 1 of 5 fluid categories. Fluid category 5 is the most serious contamination risk; fluid category 1 is the least – equivalent to wholesome drinking water. The degree of backflow risk is dependent on local circumstances. Risk assessments, if not carried out by us, should be confirmed by us.

Fluid category 5 is defined as fluid representing a serious health hazard because of the concentration of disease-causing (pathogenic) micro-organisms, radioactive or very toxic substances, including any fluid that contains:

a) faecal material or any other human waste

b) butchery or other animal waste, or

c) pathogens from any other source

Fluid 5 backflow risks are likely to include fire hose reels (where the hose outlets could be immersed in drains etc), hose pipes on hose union taps, pressurised sewage, cooling systems and uncovered water storage for fire-fighting purposes.

The Byelaws require every backflow risk to be protected by a recognised backflow prevention device which has a fluid category rating at least equal to that of the contaminants which may be present.