Private Water Supply Sampling Records: What to Keep

1. Statutory record vs operator file

It is useful to separate two different things that are often described loosely as “sampling records”. First, Regulation 14 requires the local authority to maintain a formal record of each private water supply in its area. DWI's Regulation 14 guidance says that record includes the monitoring programme and, within 28 days of information becoming available, the date, results and location of sampling and analysis and the reason the sample was taken.

Second, an owner, operator, relevant person, estate manager or consultant will usually benefit from keeping a practical working file of the same sampling activity. That file helps you understand trends, prepare for risk assessment, answer questions from a buyer or insurer, investigate failures and show what happened after a problem. It should complement the local authority and laboratory records, not be presented as the statutory record itself.

2. Record the monitoring programme

Keep the current monitoring programme or sampling schedule supplied or agreed by the local authority. Do not recreate regulatory frequencies from memory. The programme should tell you what type of monitoring is expected and help distinguish a planned compliance visit from a voluntary operational check or an investigation.

DWI's Regulation 7 guidance explains that monitoring depends on the supply type. Regulation 9 supplies require Group A and Group B monitoring at prescribed frequencies, together with any additional monitoring arising from risk assessment. Regulation 10 supplies, other than single-dwelling supplies, have a different monitoring regime. Regulation 8 monitoring is risk-assessment led. Your sampling record should therefore record the purpose of this particular sample rather than relying on a generic label such as “annual test”.

3. Record each sampling event

A useful sampling event should be understandable years later by somebody who was not present. Record the supply or site, date, the precise sample point and the reason for sampling. DWI's Regulation 14 guidance specifically refers to the date, results, location and reason. It gives examples including routine programmed compliance sampling, risk-assessment sampling, investigation of a failure, an owner or occupier request, a complaint or an operational incident.

For your own operational file it is also sensible to retain, where available, the sample or laboratory reference, sampler or sampling organisation, laboratory, parameter suite, collection time, relevant field observations and the file name or link for the laboratory certificate. These additional details are practical evidence rather than a claim that every one is a separate statutory field imposed on an operator.

4. Identify the sampling point precisely

“Kitchen tap” can be too vague on a shared or distributed supply. Record the property, room or outlet clearly enough that another person could locate it. For example: “Cottage 3 – kitchen cold tap” or “Main café – preparation sink cold tap”. If there are storage tanks, branches or different treatment trains, the exact point may be important to understanding where a problem entered the system.

Regulation 12 and DWI guidance require regulatory sampling to represent the water being consumed. In many cases the point is a kitchen tap, but it can differ, for example where water is used in food manufacture. A regulatory sample is not automatically required from every property on a shared supply; the point should represent the supply and the risk being assessed. Consistent naming also makes trend reviews much easier.

5. Record purpose, Group A/B and investigations

Where the sample forms part of Regulation 9 monitoring, record whether it was collected for Group A or Group B monitoring if that information is provided. DWI's current reporting guidance makes that distinction important because the reason explains which specification the parameters were tested against.

Other useful purpose labels include Regulation 8 risk-based monitoring, Regulation 10 monitoring, additional parameters arising from risk assessment, investigation, complaint, incident, voluntary operational check, pre-purchase request or follow-up/resample. Avoid inventing a regulatory classification if you do not know it: retain the local authority or laboratory wording and ask for clarification instead.

6. Keep the original laboratory report

Keep the original laboratory PDF, certificate or official result record alongside any summary you maintain. A dashboard can make results easier to search and compare, but it should never become the only evidence. The original report contains the laboratory's parameter names, units, limits or reference information, result qualifiers and identifiers that can be lost when somebody manually copies numbers into a spreadsheet.

Use a stable naming convention such as 2026-08-14_MainHouse_KitchenTap_LabRef12345.pdf, and link that file from the sampling event. If the council sends a covering email explaining the regulatory significance, keep that with the result as well.

7. Keep results in context

A laboratory number without context is easy to misread. Record the units exactly as reported and avoid silently converting values. If your system displays pass/fail or an alert, make it clear whether that status comes from the laboratory/local authority or is merely an internal workflow flag.

Keep notes that explain circumstances that may matter later, such as a treatment unit being out of service, a recently replaced filter, unusually low occupancy, a supply interruption or a different sampling point. Do not use those notes to dismiss a result; their purpose is to help the competent people investigating the supply understand the event.

8. Failures and repeat samples

When a result does not meet a standard or indicator value, do not overwrite it with the later repeat result. Keep the original result as the parent event and link the investigation, advice, corrective action, notices if any, and repeat samples back to it.

DWI Regulation 7 guidance says that where a sample exceeds a standard, the local authority must investigate under Regulation 16. Additional repeat testing may form part of that investigation, but the authority should not rely on repeat sampling alone to decide whether a supply is wholesome or potentially dangerous to health. That is why a clean repeat result should not erase the evidence trail around the first failure.

9. Retention and history

Sampling data becomes more valuable as a time series. A single test is a snapshot; several years of consistent records can reveal recurring seasonal issues, changes after treatment work, repeated failures at one branch or the effect of a source change. Preserve the original reports and avoid renaming sampling points in a way that breaks that history.

When a property is sold, a manager changes or a consultant hands work back to the owner, include a sampling index showing where the original reports are stored. If you replace a spreadsheet or database, keep an export or migration record so older results remain traceable.

10. Practical sampling-record template

A practical operator record can use the following structure. Not every field is a statutory requirement on an operator; the purpose is to create an evidence trail that remains understandable.

11. Common record-keeping mistakes

• Keeping only a spreadsheet: useful for trends, but weak if the original laboratory certificate cannot be produced.
• Using vague sample points: “tap” or “house” may be impossible to interpret on a multi-building supply.
• Calling every sample an annual test: this loses the distinction between Group A, Group B, risk-based and investigation sampling.
• Deleting failed results after a clear repeat: this destroys the investigation trail.
• Mixing voluntary checks with regulatory samples: both can be useful, but label them accurately so nobody assumes a voluntary test satisfies the local authority programme.
• Copying regulatory frequencies into a static document: retain the current programme from the authority because the programme can change with supply classification, volume, risk assessment or regulatory decisions.

12. Frequently asked questions