Regulation 10 Private Water Supplies in England

1. What Regulation 10 covers

Regulation 10 of the Private Water Supplies (England) Regulations 2016, as amended, covers what DWI calls “other private supplies”. In practical terms, it includes private supplies that do not fall within Regulation 8 further distribution and do not meet the Regulation 9 large, commercial or public-use criteria.

DWI describes two important Regulation 10 situations: a supply using less than 10 m³ per day for domestic purposes where the water is not supplied as part of a commercial or public activity, and a private supply serving a single dwelling. These two situations sit under the same regulation but are not treated identically for routine risk assessment and monitoring.

2. Regulation 8, 9 or 10?

Before applying any monitoring rule, establish which category actually describes the supply:

• Regulation 8: water originating from a public water company is further distributed through a third party's private network to consumers who are not the water company's direct customer.
• Regulation 9: private supplies providing 10 m³/day or more for domestic purposes, or supplying water as part of a commercial or public activity regardless of volume.
• Regulation 10: private supplies outside those categories, including smaller non-commercial shared supplies and single dwellings.

Use the supply category helper as a prompt only, then retain the local authority's classification. The tool cannot make the statutory determination.

3. Small shared Regulation 10 supplies

A common Regulation 10 arrangement is one source supplying several owner-occupied or otherwise non-commercial properties, with average domestic use below 10 m³/day. DWI's broad rule of thumb, where volume is not metered, is around 200 litres per person per day; 10 m³/day is therefore roughly equivalent to 50 people for normal domestic use.

That estimate is a classification aid, not a reason to ignore actual metered or occupancy information. If the number of users, buildings or uses changes, record it and ask the local authority whether the category remains correct.

For a shared supply, keep the practical governance alongside the regulatory record: who owns the source, who can access treatment equipment, how maintenance and electricity are paid, who receives council correspondence and how emergency decisions are communicated. The shared-supply responsibilities guide deals with those operational arrangements in more detail.

4. The single-dwelling exception

A Regulation 10 supply serving only one dwelling has a specific exception. DWI states that these single-dwelling supplies do not require routine regulatory monitoring and risk assessment unless the owner or occupier asks the local authority to carry them out.

That does not mean a single-dwelling supply can be assumed safe or that the authority has no role. If the local authority suspects a potential danger to health it can investigate, and DWI recommends sampling as part of an investigation where appropriate. Owners can also request risk assessment and/or monitoring from the authority.

5. Risk assessment

For Regulation 10 supplies other than the single-dwelling exception, the local authority's Regulation 6 risk assessment is a whole-system review from source through treatment, storage and distribution to the point of use. DWI's England guidance requires applicable private supplies to be risk assessed at least every five years, with earlier review where the authority considers the existing assessment inadequate or circumstances have changed significantly.

The five-year date should not become a reason to ignore a known change. Source deterioration, new treatment, alterations to storage or distribution, increased occupancy and a new use of a building can all affect risk and should be recorded when they happen. The dedicated Regulation 6 risk-assessment guide explains the statutory assessment separately.

6. Five-year monitoring

DWI states that Regulation 10 supplies other than single dwellings must be monitored by the local authority at least once every five years, and more frequently if the risk assessment indicates this is necessary. This is a minimum regulatory frequency, not a promise that every supply will only be sampled once in five years.

The local authority may need additional or more frequent samples because of source vulnerability, treatment performance, previous results, changes to the system or another risk identified through the assessment. Keep the official monitoring programme and laboratory reports rather than relying on an assumed repeating date.

7. The five specified parameters

For Regulation 10 supplies other than single dwellings, DWI lists five specified parameters for routine regulatory monitoring:

These parameters do not make the risk assessment redundant. The risk assessment determines whether other regulated or health-relevant parameters also need monitoring.

8. Additional risk-based monitoring

DWI's Regulation 10 guidance requires the local authority to monitor other Schedule 1 parameters where the risk assessment identifies a risk of non-compliance or a potential danger to health. That is why two Regulation 10 supplies can have different laboratory schedules even though both share the same five core parameters.

Examples might include parameters associated with local geology, agriculture, plumbing materials or the treatment process, but the actual monitoring decision belongs to the local authority's regulatory programme. Do not construct a statutory test suite by copying another property's report.

9. Why Group A and Group B do not apply

Group A and Group B are Regulation 9 monitoring concepts. DWI explicitly states that Regulation 10 supplies are not subject to Group A and Group B monitoring. Instead, the five specified parameters and any additional risk-based parameters apply.

This distinction matters when reading council schedules or laboratory reports. A shared Regulation 10 supply is not “missing its Group B test” simply because Group B terminology does not appear. See the Group A vs Group B guide for the Regulation 9 regime.

10. Change of use can change classification

A Regulation 10 classification should not be treated as permanent if the way water is used changes. A property becoming a holiday let, hospitality business or other commercial/public premises can move the supply into Regulation 9. Tenanted properties require particular care: DWI sets out criteria that consider the commercial nature of the letting and who has responsibility and control over the water supply.

Likewise, a shared supply that grows to 10 m³/day or more for domestic purposes falls within the Regulation 9 volume threshold. Record the date and nature of a change and ask the local authority to confirm the classification rather than assuming the old category still applies.

11. New and reinstated supplies

Regulation 13 deals with new private supplies and supplies reinstated after 12 months of non-use. DWI says a local authority should become involved as soon as it is aware of a new or reinstated supply and determine the appropriate Regulation 8, 9 or 10 monitoring regime.

Single dwellings remain a special case: DWI's Regulation 13 guidance says the routine Regulation 6 assessment and Regulation 10 monitoring obligations are not automatically imposed on a single non-commercial dwelling, but the authority should make preliminary enquiries and must investigate if it suspects the water may be unwholesome or present a potential danger to health.

12. Records worth keeping

These records do not create compliance by themselves, but they make it easier to understand the history of the supply and respond to the local authority, buyers, neighbours or contractors without reconstructing events from memory.

13. Common mistakes

• Assuming “under 10 m³/day” automatically means Regulation 10. Commercial/public use can still make it Regulation 9.
• Treating a single dwelling like a shared Regulation 10 supply. The routine monitoring and risk-assessment exception matters.
• Expecting Group A and Group B. Those groups are for Regulation 9, not Regulation 10.
• Assuming five years means no action between visits. A risk assessment can justify more monitoring and significant change can require earlier review.
• Ignoring change of use. Tenancy, holiday letting, business use or increased volume may alter classification.
• Using private testing as a replacement for local-authority regulatory functions. Private testing may be useful operationally but does not remove the authority's statutory role where regulatory assessment or monitoring is required.

14. Frequently asked questions