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What do the water quality zone report results mean?

The water quality zone reports contain information about the quality of your water.

We collect samples at all stages of distribution from treatment works, service reservoirs, and at customers properties. The samples are analysed in a laboratory to ensure they comply with drinking water safety standards.

Our area is divided into 19 water quality zones. Each of these zones is supplied either by a single source or a group of sources that are blended within service reservoirs.

Click here to find your Water Quality Zone report

Our area is divided into 19 water quality zones, find your report here.

Find out what the technical terms used in the Water Quality Reports mean.


The name of the zone (e.g Shavers End 2) and type of parameter (test) covered by the report.


The concentration or value is expressed in different units. Most of the parameters sampled are in milligrams per litre (mg/l) or micrograms per litre (µg/l). These are very small amounts. One mg/l is one part in 1,000,000 parts of water (or 0.0001%). One µg/l is one part in 1,000,000,000 parts of water (or 0.0000001%)

Prescribed Concentration or Value (PCVs)

These standards are set down in the Water Supply (Water Quality) Regulations 2000 in line with European (EC) requirements. They are the acceptable levels of certain elements, compounds or substances which are allowed in drinking water. Usually this is a maximum allowed level but occasionally it can be a minimum allowed level.

Number of samples

This is the number of samples collected from the zone during a period of time, usually the previous 12 months.

Number of samples > PCV

This is the number of samples that has breached a parameter limit or PCV.
% > PCV This column shows the percentage of results, which failed the standard for each parameter sampled. This is expressed as a percentage of the total number of samples for that parameter. For example, 2% shows that 1 sample in 50 failed. In most cases you will see a value of 0, which demonstrates that the water has met the standard every time a sample was collected.

Maximum, mean and minimum

This demonstrates a summary of the results from the tests over the time period. The minimum, mean and maximum concentrations are shown. The < symbol shows that the value recorded was below measurable limits. The mean is calculated by adding up all the results and dividing it by the total number of tests for that parameter.

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