Last edited 13 May 2019

Types of water

Approved Document G (Sanitation, hot water safety and water efficiency), 2015 edition, defines a number of classifications of water.

Domestic hot water: water that has been heated for cooking, food preparation, personal washing or cleaning purposes. The term is used irrespective of the type of building in which the hot water system is installed.

Greywater: domestic wastewater excluding faecal matter and urine. When appropriately treated this may replace the use of wholesome water in wcs, urinals, irrigation or washing machines.

Harvested rainwater: rainwater harvested from roofs or other suitable surfaces and collected and stored. When appropriately treated this may replace the use of wholesome water in WCs, urinals irrigation or washing machines.

Heated wholesome water: water that, when cold, was wholesome in accordance with the definition (of wholesome water) and has been subjected to a heat source to increase its temperature.

Softened wholesome water: water which would be regarded as wholesome for the purposes of the regulations made under Section 67 of the Water Industry Act 1991 (Standards of wholesomeness) as they apply for the purposes of Part G of Schedule 1 in accordance with paragraph (2c) but for the presence of sodium in excess of the level specified in those regulations if it is caused by a water softener or water softening process which reduces the concentration of calcium and magnesium.

Wholesome water: water complying with the requirements of regulations made under Section 67 (Standards of wholesomeness) of the Water Industry Act 1991. The regulations made under this Section at the time of publication of this Approved Document are; for England, the Private Water Supplies Regulations 2009 (SI 2009/3101), for Wales the Private Water Supplied (Wales) Regulations (SI 2010/66) and for England the Water Supply (Water Quality) Regulations 2000 (SI 2000/3184 as amended), and, for Wales, the Water Supply (Water Quality) Regulations 2001 (SI 2001/3911 as amended).

The document also refers to:

Other definitions of water types might include:

Black water, brown water or sewage: Water that has come into contact with faecal matter or urine.
Foul water: waste from a sanitary convenience, bidet or appliance used for washing receptacles for foul waste; or water which has been used for food preparation, cooking or washing.
White water, potable water, clean water or fresh water: water that is of drinking water quality.
Non-potable water: water that is not of drinking water quality.
Mains water.
Waste water: Water that has been used in homes, businesses, industry and so on.
Sewage refers specifically to a mixture of waste water and excrement.
Drinking water.
Rainwater.
Hard water is found in areas which have a chalk and limestone geology and has a high level of naturally-occurring calcium and magnesium compounds.
Soft water has a low level of naturally-occurring calcium and magnesium compounds.