UK Department of the Environment, Transport and the Regions

Drinking Water 1999

A report by the Chief Inspector
Drinking Water Inspectorate

Definitions and Glossary of Terms

After-growth the growth of microorganisms within distribution systems.

Aquifer water-containing underground strata.

Authorities the Secretary of State for the Environment, Transport and the Regions, or the National Assembly for Wales, as the context may require

Badenoch Reports the first (1990) and second (1995) reports of the Group of Experts on Cryptosporidium in Water Supplies

Biofilm naturally occurring growth of micro-organisms on surfaces inside water mains

Bouchier Report the third (1998) report of the Group of Experts on Cryptosporidium in Water Supplies

Bulk supply water supplied in bulk, usually in treated form, from one water company to another.

CCM Committee on Chemicals and Materials for Use in Public Water Supply and Swimming Pools

Coliforms a group of generally harmless bacteria which may be faecal or environmental in origin.

Compliance assessment a comparison made by the Inspectorate of data gathered by water companies against standards and other regulatory requirements.

Compliance programme a programme of works required as part of an undertaking

Contravention a breach of a regulatory requirement.

Cryptosporidium a protozoan parasite.

Determination an analysis for a specific parameter.

Distribution systems a water company's network of mains, pipes, pumping stations and service reservoirs through which treated water is conveyed to consumers.

DWI website See Websites

EC Drinking Water Directive Council Directive 80/778/EEC relating to the quality of water intended for human consumption. (Replaced by Council Directive 98/83/EC in December 1998 - the "New Directive")

Enforcement action the means, as set out in the Water Act 1989 and consolidated into the Water Industry Act 1991, by which the Secretary of State requires a water company to comply with certain regulatory requirements.

Epidemiology a process of studying the distribution of cases of disease within a population in relation to exposure to possible sources of the infection, with a view to establishing the actual source of the infection

Epoxy resin relining a rehabilitation process in which a cleaned section of iron water main is sprayed with a mixture of epoxy resin and hardener to produce a thin but strong coating of material on the inside of the main.

Exceedence synonym for contravention (see above)

Faecal coliforms a sub-group of coliforms, almost exclusively faecal in origin.

Giardia a protozoan parasite.

Groundwater water from aquifers or other underground sources.

Guidance Document "Guidance on Safeguarding the Quality of Public Water Supplies". HMSO 1989 (ISBN 0 11 752262 7).

Improvement programmes improvement works, associated with undertakings or conditions of regulation 4 relaxations.

Incident an event affecting or threatening to affect drinking water quality.

Indicator organism an organism which indicates the presence of contamination and hence the possible presence of pathogens.

Inspectorate the Drinking Water Inspectorate.

Key parameters 17 parameters chosen for these Reports to indicate quality of water in supply zones.

Legal requirements the requirements as specified in the Water Act 1989, now consolidated into the Water Industry Act 1991, and the Regulations made under the Acts.

Mean zonal percentage compliance See zonal percentage compliance.

m3/d cubic metre per day.

mg/l milligram per litre.

Ml/d megalitre per day (One Ml/d is equivalent to 1,000 m3/d, or to 220,000 gallon/d).

µg/l microgram per litre.

ng/l nanogram per litre.

Notice of Intention to make a Final Order a necessary precursor to the issue of a Final Enforcement Order which must be advertised with a minimum of 28 days being allowed for representations or objections to the proposed Order.

Oocyst the resistant form in which Cryptosporidium occurs in the environment, and which is capable of causing infection.

Operational Guidelines and Code of Practice (OGCP) "In situ Epoxy Resin Lining - Operational Guidelines and Code of Practice. A source document for the Water Mains Rehabilitation Manual". I C Warren. WRc 1989.

Operational performance index the average of the mean zonal compliance for each of the six parameters most reflecting the operation and maintenance of treatment works and distribution systems.

Outbreak Control Team (OCT) A team set up to investigate possible waterborne outbreaks of cryptosporidiosis, comprising members of the medical profession, as well as representatives of relevant local authorities and water companies

Overall quality index The average of the mean zonal compliance for each of the 17 key parameters.

PAH a group of organic compounds known as polycyclic aromatic hydrocarbons, comprising for the purposes of the Regulations six substances: fluoranthene, benzo 3,4 fluoranthene, benzo 11,12 fluoranthene, benzo 3,4 pyrene, benzo 1,12 perylene and indeno (1,2,3-cd) pyrene.

Parameters the substances, organisms and properties listed in Schedule 2 and regulation 3 of the Regulations.

Pathogen an organism which causes disease.

PCV see 'Prescribed concentration or value'

Pesticides any fungicide, herbicide or insecticide or related product (excluding medicines) used for the control of pests or diseases.

pH value a measure of the acidity or basicity related to the concentration of the hydrogen ion.

Plumbosolvency the tendency for lead to dissolve in water.

Polycyclic aromatic hydrocarbons see 'PAH'

Pre and post renovation assessment (PPRA) a programme of assessment before and after mains renovation to demonstrate justification for the work, and the improvements achieved by the renovation.

Prescribed concentration or value (PCV) the numerical value assigned to water quality standards defining the maximal or minimal legal concentration or value of a parameter. In certain circumstances, the PCV may be authorised by the Secretary of State under regulation 4 to be relaxed to a specified extent - see 'Relaxation'.

Principles of Water Supply Hygiene and Technical Guidance Notes a booklet identifying principles to be considered when developing procedures for safeguarding water supplies against contamination and guidance on development of such procedures - published by WaterUK, October 1998

Private supplies water taken from private sources or supplied by non-licensed suppliers: supplies of water provided otherwise than by a statutorily appointed water undertaker.

Public record the information made available to the public as required by regulations 29 and 30.

Public supplies water supplied by a company licensed for that purpose.

Regulations the Water Supply (Water Quality) Regulations 1989, as amended, made under the Act or, in the case of private water supplies, the Private Water Supplies Regulations 1991.

Regulatory requirements see 'Legal requirements'.

Relaxation a relaxation of the standards according to regulations 4 and 5 - subject in most cases to the completion of improvement works - in emergencies or as a result of exceptional meteorological conditions or by reason of the nature and structure of the ground from which the supply emanates.

Secretary of State the Secretary of State for the Environment, Transport and the Region

Service reservoir a water tower, tank or other reservoir used for the storage of treated water within the distribution system.

Springs groundwater appearing at the surface at the outcrop of the junction of a permeable with an impermeable stratum.

Standards the prescribed concentrations or values listed in Schedule 2, Tables A to E and regulation 3 of the Regulations.

Supply point a point other than a consumer's tap authorised for the taking of samples for compliance with the Regulations

Surface water water from rivers, impounding reservoirs or other surface water source.

Technical audit the means of checking that water companies are complying with their statutory obligations.

THM a group of organic substances known as trihalomethanes, comprising for the purposes of the Regulations four substances: trichloromethane (also known as chloroform), dichlorobromomethane, dibromochloromethane and tribromomethane.

Time of supply the moment when water passes from the water company's pipework into a consumer's pipework.

Toxicology the study of the health effects of substances.

Treated water water treated for use for domestic purposes as defined in the Regulations.

Trihalomethanes see 'THM'

Undertaking a legally binding undertaking to take appropriate steps to secure or restore compliance with regulatory duties; given by a water company to the Secretary of State for the purposes of section 19(1)(b) of the Water Industry Act 1991.

Water supply zone the basic unit of supply for establishing sampling frequencies, compliance with standards and information to be made publicly available.

Websites Location of information on the Internet - the DWI website is http://www.dwi.detr.gov.uk

Wholesome/Wholesomeness a concept of water quality which is defined by reference to standards and other requirements set out in the Regulations.

WRc Water Research Centre (1989) plc and/or, as the context may require, its predecessor body.

Zonal percentage compliance The percentage of results for a specific parameter which complied with the PCV - the mean zonal percentage compliance is the average of the zonal percentage compliances of every one of a company's zones.

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Drinking Water Inspectorate,
Floor 2/A1, Ashdown House, 123 Victoria Street, London, SW1E 6DE
Telephone : 020 7944 5956 - Facsimile : 020 7944 5969
E-mail: dwi_enquiries@detr.gov.uk

Published 12 July 2000; Updated 11 July 2001
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Web site terms
© Crown copyright 2001

After-growth	the growth of microorganisms within distribution systems.
Aquifer	water-containing underground strata.
Authorities	the Secretary of State for the Environment, Transport and the Regions, or the National Assembly for Wales, as the context may require
Badenoch Reports	the first (1990) and second (1995) reports of the Group of Experts on Cryptosporidium in Water Supplies
Biofilm	naturally occurring growth of micro-organisms on surfaces inside water mains
Bouchier Report	the third (1998) report of the Group of Experts on Cryptosporidium in Water Supplies
Bulk supply	water supplied in bulk, usually in treated form, from one water company to another.
CCM	Committee on Chemicals and Materials for Use in Public Water Supply and Swimming Pools
Coliforms	a group of generally harmless bacteria which may be faecal or environmental in origin.
Compliance assessment	a comparison made by the Inspectorate of data gathered by water companies against standards and other regulatory requirements.
Compliance programme	a programme of works required as part of an undertaking
Contravention	a breach of a regulatory requirement.
*Cryptosporidium*	a protozoan parasite.
Determination	an analysis for a specific parameter.
Distribution systems	a water company's network of mains, pipes, pumping stations and service reservoirs through which treated water is conveyed to consumers.
DWI website	See Websites
EC Drinking Water Directive	Council Directive 80/778/EEC relating to the quality of water intended for human consumption. (Replaced by Council Directive 98/83/EC in December 1998 - the "New Directive")
Enforcement action	the means, as set out in the Water Act 1989 and consolidated into the Water Industry Act 1991, by which the Secretary of State requires a water company to comply with certain regulatory requirements.
Epidemiology	a process of studying the distribution of cases of disease within a population in relation to exposure to possible sources of the infection, with a view to establishing the actual source of the infection
Epoxy resin relining	a rehabilitation process in which a cleaned section of iron water main is sprayed with a mixture of epoxy resin and hardener to produce a thin but strong coating of material on the inside of the main.
Exceedence	synonym for contravention (see above)
Faecal coliforms	a sub-group of coliforms, almost exclusively faecal in origin.
*Giardia*	a protozoan parasite.
Groundwater	water from aquifers or other underground sources.
Guidance Document	"Guidance on Safeguarding the Quality of Public Water Supplies". HMSO 1989 (ISBN 0 11 752262 7).
Improvement programmes	improvement works, associated with undertakings or conditions of regulation 4 relaxations.
Incident	an event affecting or threatening to affect drinking water quality.
Indicator organism	an organism which indicates the presence of contamination and hence the possible presence of pathogens.
Inspectorate	the Drinking Water Inspectorate.
Key parameters	17 parameters chosen for these Reports to indicate quality of water in supply zones.
Legal requirements	the requirements as specified in the Water Act 1989, now consolidated into the Water Industry Act 1991, and the Regulations made under the Acts.
Mean zonal percentage compliance	See zonal percentage compliance.
m3/d	cubic metre per day.
mg/l	milligram per litre.
Ml/d	megalitre per day (One Ml/d is equivalent to 1,000 m3/d, or to 220,000 gallon/d).
µg/l	microgram per litre.
ng/l	nanogram per litre.
Notice of Intention to make a Final Order	a necessary precursor to the issue of a Final Enforcement Order which must be advertised with a minimum of 28 days being allowed for representations or objections to the proposed Order.
Oocyst	the resistant form in which Cryptosporidium occurs in the environment, and which is capable of causing infection.
Operational Guidelines and Code of Practice (OGCP)	"In situ Epoxy Resin Lining - Operational Guidelines and Code of Practice. A source document for the Water Mains Rehabilitation Manual". I C Warren. WRc 1989.
Operational performance index	the average of the mean zonal compliance for each of the six parameters most reflecting the operation and maintenance of treatment works and distribution systems.
Outbreak Control Team (OCT)	A team set up to investigate possible waterborne outbreaks of cryptosporidiosis, comprising members of the medical profession, as well as representatives of relevant local authorities and water companies
Overall quality index	The average of the mean zonal compliance for each of the 17 key parameters.
PAH	a group of organic compounds known as polycyclic aromatic hydrocarbons, comprising for the purposes of the Regulations six substances: fluoranthene, benzo 3,4 fluoranthene, benzo 11,12 fluoranthene, benzo 3,4 pyrene, benzo 1,12 perylene and indeno (1,2,3-cd) pyrene.
Parameters	the substances, organisms and properties listed in Schedule 2 and regulation 3 of the Regulations.
Pathogen	an organism which causes disease.
PCV	see 'Prescribed concentration or value'
Pesticides	any fungicide, herbicide or insecticide or related product (excluding medicines) used for the control of pests or diseases.
pH value	a measure of the acidity or basicity related to the concentration of the hydrogen ion.
Plumbosolvency	the tendency for lead to dissolve in water.
Polycyclic aromatic hydrocarbons	see 'PAH'
Pre and post renovation assessment (PPRA)	a programme of assessment before and after mains renovation to demonstrate justification for the work, and the improvements achieved by the renovation.
Prescribed concentration or value (PCV)	the numerical value assigned to water quality standards defining the maximal or minimal legal concentration or value of a parameter. In certain circumstances, the PCV may be authorised by the Secretary of State under regulation 4 to be relaxed to a specified extent - see 'Relaxation'.
Principles of Water Supply Hygiene and Technical Guidance Notes	a booklet identifying principles to be considered when developing procedures for safeguarding water supplies against contamination and guidance on development of such procedures - published by WaterUK, October 1998
Private supplies	water taken from private sources or supplied by non-licensed suppliers: supplies of water provided otherwise than by a statutorily appointed water undertaker.
Public record	the information made available to the public as required by regulations 29 and 30.
Public supplies	water supplied by a company licensed for that purpose.
Regulations	the Water Supply (Water Quality) Regulations 1989, as amended, made under the Act or, in the case of private water supplies, the Private Water Supplies Regulations 1991.
Regulatory requirements	see 'Legal requirements'.
Relaxation	a relaxation of the standards according to regulations 4 and 5 - subject in most cases to the completion of improvement works - in emergencies or as a result of exceptional meteorological conditions or by reason of the nature and structure of the ground from which the supply emanates.
Secretary of State	the Secretary of State for the Environment, Transport and the Region
Service reservoir	a water tower, tank or other reservoir used for the storage of treated water within the distribution system.
Springs	groundwater appearing at the surface at the outcrop of the junction of a permeable with an impermeable stratum.
Standards	the prescribed concentrations or values listed in Schedule 2, Tables A to E and regulation 3 of the Regulations.
Supply point	a point other than a consumer's tap authorised for the taking of samples for compliance with the Regulations
Surface water	water from rivers, impounding reservoirs or other surface water source.
Technical audit	the means of checking that water companies are complying with their statutory obligations.
THM	a group of organic substances known as trihalomethanes, comprising for the purposes of the Regulations four substances: trichloromethane (also known as chloroform), dichlorobromomethane, dibromochloromethane and tribromomethane.
Time of supply	the moment when water passes from the water company's pipework into a consumer's pipework.
Toxicology	the study of the health effects of substances.
Treated water	water treated for use for domestic purposes as defined in the Regulations.
Trihalomethanes	see 'THM'
Undertaking	a legally binding undertaking to take appropriate steps to secure or restore compliance with regulatory duties; given by a water company to the Secretary of State for the purposes of section 19(1)(b) of the Water Industry Act 1991.
Water supply zone	the basic unit of supply for establishing sampling frequencies, compliance with standards and information to be made publicly available.
Websites	Location of information on the Internet - the DWI website is http://www.dwi.detr.gov.uk
Wholesome/Wholesomeness	a concept of water quality which is defined by reference to standards and other requirements set out in the Regulations.
WRc	Water Research Centre (1989) plc and/or, as the context may require, its predecessor body.
Zonal percentage compliance	The percentage of results for a specific parameter which complied with the PCV - the mean zonal percentage compliance is the average of the zonal percentage compliances of every one of a company's zones.

Drinking Water 1999

A report by the Chief InspectorDrinking Water Inspectorate

Definitions and Glossary of Terms

A report by the Chief Inspector
Drinking Water Inspectorate