Regulation 9 Private Water Supplies in England: Operator Guide

1. What Regulation 9 covers

Regulation 9 of the Private Water Supplies (England) Regulations 2016, as amended, covers large private supplies and supplies where private water is used as part of a commercial or public activity. This is the category that commonly catches holiday accommodation, hospitality, food businesses, visitor facilities and larger shared supplies.

The classification matters because Regulation 9 brings a structured monitoring programme under Schedule 2 as well as the source-to-tap risk-assessment duties that apply to regulated supplies. It is therefore more than a label for “business water”: it determines how the local authority assesses and monitors the supply.

2. The two Regulation 9 routes

DWI's Regulation 9 guidance gives two separate routes into this category:

• Volume: the supply provides an average of 10 m³/day or more for domestic purposes. DWI uses approximately 50 people as a practical equivalent where volume cannot be established.
• Use: private water is used as part of a commercial or public activity. This route applies irrespective of the volume consumed.

That means a small holiday cottage or café can be Regulation 9 even though it uses far less than 10 m³/day, while a large non-commercial shared supply can be Regulation 9 because the volume threshold is exceeded.

3. Commercial and public activity

DWI lists a wide range of examples where Regulation 9 can apply, including cafés, pubs, restaurants, hotels, guest houses, campsites, schools, nurseries, universities, museums, sports and leisure facilities, tourist attractions and other premises where private water is made available to the public for human consumption.

Private water used in rented accommodation is also treated by DWI as commercial activity. In practice this means landlords, holiday-let operators and guest-accommodation businesses should not assume that a low-volume supply is outside Regulation 9.

For detailed accommodation or food-business issues, use the dedicated guides rather than trying to turn this overview into sector-specific advice: holiday lets and guest accommodation, Airbnb and short-term lets, and restaurants and cafés.

4. Not every business use is Regulation 9

A common mistake is to classify a supply purely because it serves a business address. DWI says the legislation is concerned with how the private water is consumed, not simply whether the building itself is commercial.

For example, DWI's Regulation 9 guidance says a business office where workers only use the supply for domestic purposes, such as making drinks in a free staff area, will not normally be Regulation 9 solely because it is an office if the volume is below 10 m³/day. But if private water becomes part of a product or service sold for a fee, Regulation 9 can apply.

This is one reason online category checkers should be treated as prompts rather than legal determinations. Record the local authority's conclusion for the actual supply, especially where the use is unusual or changes over time.

5. Shared supplies and mixed use

Where one source and treatment system serves several buildings, classification is determined at supply level. DWI's Regulation 7 and Regulation 12 guidance states that if water at one or more buildings on the supply is used as part of a commercial or public activity, the entire supply is monitored in accordance with Regulation 9.

That prevents a mixed-use estate from being split artificially into “commercial” and “domestic” regulatory categories when the buildings share the same private water supply. Operators should keep a current source-to-tap schematic showing which premises, treatment stages and distribution branches are part of the same supply.

6. Regulation 6 risk assessment

The statutory risk assessment is a local-authority duty. DWI describes Regulation 6 as a whole-system, source-to-tap approach that looks for hazards and control failures rather than relying on end-point sampling alone.

For an applicable Regulation 9 supply, the assessment covers the source and catchment, abstraction or collection, storage, treatment, distribution and points of use. It must be reviewed at least every five years, and DWI guidance supports earlier review where significant change or new information makes the existing assessment inadequate.

Operators should make that process easier by maintaining current source information, treatment specifications, service history, alarms, schematic drawings, access arrangements, previous laboratory results and evidence that earlier recommendations were completed. See the detailed Regulation 6 risk-assessment guide.

7. Group A and Group B monitoring

Regulation 9 is the supply category that uses Group A and Group B monitoring. The local authority must carry out both groups at the frequencies set by Schedule 2 and include any additional parameters identified by the risk assessment.

DWI explains that there are core Group A parameters that apply to every Regulation 9 supply, with other Group A parameters included only where the relevant treatment or source circumstances exist. Group B covers the remaining regulated parameters. It is therefore misleading to copy a short fixed “Regulation 9 test list” from the internet and assume it applies unchanged to every supply.

For the detailed parameter split, use the Group A vs Group B monitoring guide. For the broader sampling process, see testing and sampling in England.

8. Monitoring frequency and volume

The monitoring frequency is not simply “annual”. DWI's Regulation 7 guidance sets separate Group A and Group B frequencies according to the volume of water consumed for domestic purposes. At the smallest Regulation 9 volumes, both groups have a minimum frequency of once per year; larger supplies require more frequent monitoring.

The local authority can also increase monitoring or add parameters where the risk assessment shows this is appropriate. Under specified conditions in the amended Regulations, frequency for some parameters may be reduced or monitoring ceased after sufficient compliant historical data and a supporting risk assessment; E. coli is specifically protected from those reductions.

9. Representative sampling points

Regulation 12 requires regulatory samples to be taken at appropriate representative points. DWI says this is normally a tap used for human consumption, often a kitchen tap, while water used in food production should be sampled where it is used in the manufacturing process.

On a supply serving several buildings, the authority does not normally need to sample every property on every visit. A suitable point should represent the water being consumed and the risks identified in the assessment; locations can be rotated over time. Separate treatment systems or particular hazards may justify more than one sample.

Sampling records should identify the point used so that future results can be compared meaningfully. See what to keep in sampling records.

10. What operators manage between samples

A compliant sample is only a snapshot. Regulation 9 operators still need to manage the controls that keep the supply reliable between council visits:

These are operational records rather than a substitute for statutory monitoring. Together with the regulatory results they create the history needed to understand why a result changed and whether controls were working.

11. Failed or concerning results

If monitoring shows a breach, DWI states that the local authority must investigate under Regulation 16. Additional repeat testing may be part of that investigation, but repeat sampling alone is not enough to determine the cause or decide whether the supply is wholesome or presents a potential danger to health.

The investigation should feed back into the supply's risk assessment and corrective actions. Where health protection or formal notices are required, the local authority follows the relevant regulatory route. The dedicated failed-test guide and Regulation 18 notices guide cover those stages in more detail.

12. Changes that should trigger review

Regulation 9 management should not sit unchanged for five years where the supply has materially changed. Record changes such as:

• a dwelling becoming rented, holiday accommodation or public-facing premises;
• a new café, campsite, school, food process or other commercial/public use joining the supply;
• additional buildings, occupancy or water demand that changes the volume band;
• a new source, borehole, spring chamber, tank, treatment process or distribution branch;
• significant treatment failure, contamination event or recurring adverse trend;
• ownership, control or responsibility changes affecting access and maintenance.

Use a change log so the local authority and future operators can see what changed, when, why and what follow-up was completed.

13. Records worth keeping

For a broader document structure, use the private water supply record-keeping checklist and evidence-pack guide.

14. Common mistakes

• Assuming Regulation 9 only means “more than 10 m³/day”. Commercial or public use is a separate route and applies irrespective of volume.
• Assuming every business address is automatically Regulation 9. DWI focuses on how the private water is used.
• Classifying buildings separately on one shared supply. Commercial/public activity in one or more buildings can make the whole supply Regulation 9 for monitoring purposes.
• Calling the monitoring programme “an annual water test”. Group A and Group B frequencies vary with volume and risk.
• Sampling every property by default. The regulatory point should be representative; extra locations are risk-based.
• Relying on laboratory results without operational records. Sampling is a snapshot, not a replacement for source, treatment and maintenance control.
• Waiting for the next five-year review after a major change. Significant change should be recorded and raised with the local authority.

15. Frequently asked questions