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