Scientific services

If you run a business that requires you to regularly monitor your private water supply, we can help through our sampling and analytical service.

What do we offer?

We schedule and carry out a regulatory sampling programme for the water and sewerage services we provide to our customers. We also provide sampling and analytical services to:

  • businesses with private water supplies, including caravan and camping sites, hotels and bed and breakfast premises
  • local authorities
  • drinking water providers
  • environmental consultants
  • those requiring an analysis of a private water supply required by mortgage lenders as part of a Home Information Pack.

What is the service for?

Our range of analyses enables you to show compliance with the following regulations and their subsequent updates:

  • The Water Supply (Water Quality) Regulations 2016
  • Microbiology of Drinking Water
  • Private Water Supply Regulations 2016.

Delivered from our laboratory - ISO 17025(2017) by the United Kingdom Accreditation Service (UKAS) - our comprehensive analytical service for potable (drinking) water covers:

  • microbiological including cryptosporidium
  • general chemicals
  • metals
  • organic chemistry
  • nutrients analysis.

What is a deviating sample?

The UKAS guidance states that samples will be labelled as deviating if:

  • no time or date of sampling has been supplied
  • the sample is in the incorrect container
  • the sample has not been correctly preserved
  • the container has been incorrectly filled
  • the sample age exceeds the stability time.

If a sample is deviating, the validity of the results is in doubt. Samples will be assessed at the laboratory. This will include the container(s), its filling, preservation, the age of the sample and all the correct information supplied.

Samples that do not conform to these requirements will be highlighted as deviating on the reported analysis or, in extreme cases, cancelled.

Stability times have been established from detailed laboratory tests or recognised sources (principally ISO-5667-3).

A stability time is the maximum time for stability for that determinand, in that matrix (sample type). To request a listing, please email

Gross deviations will be cancelled, such as a bacteriological sample received in a non-sterile bottle.

What will you see?

The reported analysis will indicate when a test is deviating.

The following are examples of what may appear on the analysis report:

  • if no date or time is supplied: unknown sample age, results may be affected
  • if a sample is received in an incorrect container: incorrect container, results may be affected
  • if the stability time is exceeded at registration: stability time exceeded, results may be affected
  • if a determinand exceeds its stability time at analysis: stability time breached within laboratory, results may be affected.

In submitting samples to the Wessex Water Scientific Laboratory, you are accepting the requirement to follow these guidelines.

All deviating tests are analysed with the understanding that they will be paid for within our normal terms and conditions.

How you can help

Please follow the sampling guidelines. To enable us to analyse samples within the stability time, please ensure samples arrive at the laboratory on the same day as sampling.

You should also:

  • always provide correct sampling details, such as the time and date of sampling
  • use correct containers for sampling and fill according to requirements
  • ensure that samples are preserved at the time of sampling if preservative is required.
  • All samples (except soils and Legionella) should be refrigerated after sampling. This will minimise the deviations you receive and ensure the validity of your results.
Scientist looking down a microscope at Saltford Lab

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