Backflow prevention & fluid categories

What is backflow prevention?
Backflow prevention helps to protect and ensure that your potable water supply does not get contaminated or polluted by outside sources due to backflow. What backflow prevention device you need is dependant on which fluid category you are in.

What is a fluid category?
Under the water supply regulations 1999 a fluid category is the category in which fluid is rated as a risk from low to high. Category 1 being the lowest to category 5 being the highest risk.

When can backflow happen?
Backflow can happen when there is a pressure loss on the incoming flow allowing contaminants to get back into your potable water supply such as human waste, soap from dishwashers/sinks/showers, fertilisers, pesticides etc.

Legislation & Guidelines
Under the Water Industry Act 1991, property owners have a responsibility to ensure that every water system on their premises must contain adequate devices to prevent the backflow of fluid between connections of potable and non-potable water supplies.

Fluid Categories

Fluid category 1
Wholesome water supplied by a water undertaker and complying with the requirements of regulations made under section 67 of the Water Industry Act 1991(1).

Fluid category 2
Water in fluid category 1 whose aesthetic quality is impaired owing to–
(a) a change in its temperature, or
(b) the presence of substances or organisms causing a change in its taste, odour or appearance,
including water in a hot water distribution system.

Fluid category 3
Fluid which represents a slight health hazard because of the concentration of substances of low toxicity, including any fluid which contains–
(a) ethylene glycol, copper sulphate solution or similar chemical additives, or
(b) sodium hypochlorite (chloros and common disinfectants).

Fluid category 4
Fluid which represents a significant health hazard because of the concentration of toxic substances, including any fluid which contains –
(a) chemical, carcinogenic substances or pesticides (including insecticides and herbicides), or
(b) environmental organisms of potential health significance.

Fluid category 5
Fluid representing a serious health hazard because of the concentration of pathogenic organisms, radioactive or very toxic substances, including any fluid which contains–
(a) faecal material or other human waste;
(b) butchery or other animal waste; or
(c) pathogens from any other source

Further Reading
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