Guide

Testing your private water supply

Last updated: 27 February 2018

What your results mean

To make sure the water you consume is good quality, the government sets standards for water quality — the maximum level or acceptable range of substances in water.

Some are set to protect health, but others are set to prevent the water tasting, smelling or looking bad or staining laundry, sinks and baths.

Contaminant Description Acceptable range or maximum level allowed
pH This is the scientific term used to describe the acidity of the water. Low pH waters tend to be corrosive to pipework and dissolve metals, such as lead, contaminating your water. Extreme pH values are undesirable for aesthetic reasons. Drinking water should be in the range pH 6.5 to pH 9.5, where pH 7 is neutral.
E.Coli and enterococci E.coli (Escherichia Coli) is a bacterium, and a member of the coliform group. E. coli bacteria live in the intestines of warm-blooded animals including humans. If any amount of E. coli bacteria is found in a water sample, it is an indication that human sewage or animal faeces has contaminated the water supply. E.coli can cause illness in humans, and any sample failure must be taken very seriously. VTEC is a particular type of E. coli that produces a toxin/poison (called verotoxin). VTEC is an immediate health risk to individuals with potential long term consequences for kidney function, especially in young children. 0 per 100 ml
Coliforms These are a group of bacteria that are found in the environment as well as in the gut of warm blooded animals. They shouldn't be in your water supply and can be removed by an effective disinfection process. 0 per 100ml of water.
Nitrate Nitrates come from agricultural fertilisers, so these may be a risk in rural areas. 50 microgrames per litre
Iron Iron is present in many water sources, and may be used as part of the treatment process – it's less commonly used in private water supplies in Scotland. Increased levels of iron are most likely to occur due to the corrosion of old iron pipes. So you should remove iron pipes from your home. 200 microgrammes per litre
Manganese Manganese occurs naturally in some water sources, where it's dissolved from the surrounding rocks and enters the water supply. High concentrations of manganese in tap water may cause black discolouration. 50 microgrammes per litre
Aluminium Aluminium occurs naturally in water supplies where acidic waters dissolve it from soils and rocks. 200 microgrammes per litre
Lead Lead is not normally present in water sources in Scotland. But using lead pipes or lead joints can contaminate your water. Lead poisoning is serious and can severely affect infants neurological development. You should remove all lead pipes from your home as soon as possible. 10 microgrammes per litre
Colour Colour, in relation to water supplies, has a precise definition. It is a measure of the extent to which the water appears coloured or tinted due to substances dissolved in the water. Colour is an aesthetic concern and doesn't have any health significance, although highly coloured water won't be acceptable to consumers. You can remove the compounds which cause colour by installing standard water treatment processes. Water should be acceptable to consumers with no sudden changes.
Turbidity Turbidity is the extent to which the water appears cloudy or hazy. But it's mainly an aesthetic concern. High turbidities might indicate a problem with the treatment. Water should be acceptable to consumers with no sudden changes. High levels of turbidity will interfere with the UV effectiveness, so it needs to be controlled.
Copper Copper is a reddish-brown metal that has many industrial applications. The primary source in drinking water is the corrosion of copper plumbing materials in homes. People with chronic liver disease are potentially sensitive to copper levels in drinking water. Water with high levels of cooper can cause stomach upsets and has an unpleasant taste. 2.0 milligrams per litre. High levels of copper can interfere with UV effectiveness.
Nickel Small amounts of nickel are often found in ground water because of its presence in rocks. The most common harmful health effect of nickel in humans is an allergic reaction. The most common reaction is a skin rash at the site of contact. 20 micrograms per litre
Testing your private water supply
What your results mean