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Water quality

Last updated 16 October 2013

The Council is responsible for monitoring the quality of borough groundwater and the water in our lakes and ponds. This includes issues such as sewage treatment and disposal, bathing waters, dangerous substances, nitrates from agricultural sources, and economic instruments for water pollution.

The quality of water in rivers and streams is regulated by the Environment Agency. They can be contacted at

Drinking water quality

Results of drinking water sampling are compared with the limits set out in the Water Supply (Water Quality) Regulations 2000 (England). Below are comments on a few selected water quality parameters.

View the Thames Water drinking water quality report 2010 (1.9MB PDF file)


The pH value of water is a measurement of acidity or alkalinity. Pure water is very slightly ionised into positively charged hydrogen ions (H+) and negatively charged hydroxide ions (OH-). When water is neutral there are equal number of positive and negative ions. When there are more negative ions the water is more alkaline, conversely if the water has more positive ions it is more acidic.

The scale use to measure pH is 1 – 9; 7 is neutral less than 7 is acidic and more than 7 is alkaline. Hard water has a pH of 7.2 – pH 9.5 and soft water has a pH of 6.9 or less.

Water from the London area is hard.


The geology of London soil is mostly clay, which has a high level of calcium salts this causes the ground and surface waters to be hard. Due to the natural calcium source in the soil it is likely that the any fluctuations in calcium levels in the drinking water would be a result of natural or human activities.


Traces of fluoride occur naturally in many water sources, particularly ground water. It is not removed by conventional water treatment and some water companies artificially fluoridate water supplies as a protection against tooth decay.


Conductivity is a measurement of the ability of an aqueous solution to carry an electrical current. An ion is an atom of an element that has gained or lost an electron, which will create a negative or positive state. For example, sodium chloride (table salt) consists of sodium ions (Na+) and chloride ions (Cl-) held together in a crystal. In water it breaks apart into an aqueous solution of sodium and chloride ions. This solution will conduct an electrical current.

Total inorganic Phosphorus

Traces of phosphorus salts occur naturally in many water sources and high concentrations are associated with treated sewage effluents and agricultural fertilisers. Phosphates are also used in water treatment as a health protection measure to reduce lead content that may come from consumers' pipes. The concentrations present in water do not present any known risk to health.

Nitrate (NO3)

Nitrate occurs naturally and is present in all soils and living things. High concentrations in water maybe the result of nitrates dissolve of soils where nitrate base fertilizers have been used for crop production.

Nitrite (NO2)

Traces of nitrite are produced when chlorine and ammonia are used in the disinfection process.

In the London area chloramine, rather than free chlorine, is used as the residual disinfectant because it is more persistent in the extensive distribution system that serves the capital. The use of chloramine as the residual disinfectant involves the addition of a small amount of ammonia to the chlorinated water just before it leaves the treatment works. Traces of residual ammonia, and the chloramine itself, can be converted naturally to nitrite within the distribution system and may give rise to contraventions of the nitrite standard.

Poly-aromatic Hydrocarbons (PAH’s)

Poly-aromatic Hydrocarbons (PAH’s) are a group of approximately 10,000 compounds. Most PAH’s in the environment are from incomplete burning of carbon-containing materials like oil, wood, garbage or coal. Many useful products such as mothballs, blacktop, and creosote wood preservatives contain PAHs. They are also found at low concentrations in some special-purpose skin creams and anti-dandruff shampoos that contain coal tars.

Poly-aromatic hydrocarbons are present on coal tar linings, which were used to protect water mains before 1970. Traces of PAH’s, at concentrations that are not significant to health, are present in tap water if the original coal tar lining is still present.

Automobile exhaust, industrial emissions and smoke from burning wood, charcoal and tobacco contain high levels of PAH’s. In general, more PAH’s form when materials burn at low temperatures, such as in wood fires or cigarettes than high-temperature furnaces.

Bacteriological tests

Coliforms are a group of bacteria that maybe found in faecal matter or environment mediums such as soil or water. Faecal Streptococci belongs to a group of bacteria found almost always in faecal matter.

The total viable count is a measurement of the number of bacteria that has grown under certain laboratory conditions stated, temperature and time taken +/- 4 hours. There is no stated limit except that there should be no significant rise over a period of time.

Private Water Supply Sampling

A private water supply is any water supply which is not provided by a water company and which would not be considered to be a "mains" supply.

Most private supplies are situated in the more remote, rural parts of the country. The source of supply may well be:

  • Wells
  • Boreholes
  • Springs
  • Rivers and streams
  • Lakes or ponds

There are a couple of private water supplies that are registered with the London Borough of Waltham Forest.

If you have any questions or want advice about private water supplies, contact Environmental Health & Trading Standards on 020 8496 3000 or email

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Contact details

  • Environmental Health and Trading Standards

    Environment and Regeneration Waltham Forest Council Sycamore House Town Hall Complex Forest Road
    E17 4SU
    Phone: 020 8496 3000