- Material changes can make an existing risk assessment inadequate before the normal five-year review point.
- A new source, new commercial use, extra premises or onward distribution of mains water can affect how the supply is regulated.
- DWI recommends accurate records, maintenance diaries, plans and schematics because they support risk assessment and active management.
- For new or reinstated private supplies, Regulation 13 can require risk assessment and monitoring before domestic use begins.
Is a change log legally required?
No specific provision in the Private Water Supplies (England) Regulations 2016 requires an owner or operator to maintain a document with the title “change log”. That distinction matters. This guide should not turn good operational practice into a made-up statutory duty.
Regulation 14 requires each local authority to maintain a record of private water supplies in its area. DWI's Regulation 14 guidance says those authority records must be retained for at least 30 years and should capture the status and changes of circumstance of supplies. DWI also says authorities should note significant changes as they happen, including a revised risk assessment or installation or upgrading of a treatment process where this affects the supply's risk assessment.
Separately, DWI recommends accurate and detailed records, maintenance diaries, schematics and plans from owners and operators because that information supports the statutory risk-assessment process. That is the basis for maintaining your own change history: it is evidence and management control, not a substitute for the authority's statutory record.
- Statutory duty: the local authority must maintain the Regulation 14 record and carry out applicable Regulation 6 risk assessments.
- DWI/local-authority guidance: provide accurate information, plans, schematics and operational evidence so the supply can be assessed and regulated properly.
- Good operational practice: keep a dated change history so future users can reconstruct what the system looked like before and after an alteration.
When a change becomes material
A change is material when it can alter the hazards, controls, users, regulatory category, monitoring needs or physical route from source to tap. The key question is not whether the job was expensive. A cheap valve alteration that creates a dead leg can matter more to risk than an expensive like-for-like enclosure replacement.
Examples include changing the source, adding a borehole, switching between sources, replacing or redesigning treatment, altering storage, adding distribution branches, connecting new premises, disconnecting premises, changing public or commercial use, changing occupancy or demand materially, or changing who is responsible for operation and maintenance.
Routine maintenance still deserves a maintenance record, but it does not automatically require the same escalation as a material system alteration. Replacing a UV lamp at the manufacturer's interval is different from replacing the entire UV unit with a different model or changing the maximum flow through it.
How changes interact with Regulation 6 risk assessment
For applicable supplies in England, Regulation 6 places the statutory risk-assessment function on the local authority. DWI says the authority must assess each relevant private supply at least every five years. It also says a review should be undertaken whenever the authority considers the current assessment inadequate or circumstances have changed significantly. DWI gives deterioration of raw-water quality and installation of a new treatment process as examples.
That makes the change record useful before the five-year date. If treatment, source, storage, distribution or use changes, the operator can show the authority exactly what happened rather than relying on memory. Where the change could affect the risk picture, contact the local authority and ask whether the statutory assessment or monitoring programme needs to be revisited.
Do not write “risk assessment updated” in your own log unless you mean an internal operational review. The statutory Regulation 6 assessment is the local authority's function. Record instead what you changed, what information you sent, what advice you received and the date of any authority review.
Can a change affect Regulation 8 or Regulation 9?
Yes. In England, DWI describes Regulation 9 as covering supplies of 10 m³/day or more for domestic purposes and supplies where water is provided as part of a commercial or public activity. A domestic supply that starts serving holiday accommodation, a café, public facilities or another commercial use can therefore move into Regulation 9 even if the physical source has not changed.
Regulation 8 concerns certain further distribution arrangements where water originates from a water undertaker or licensed supplier and is then distributed by another person. Changing from a private borehole to a mains-fed private distribution network, or creating a new connection arrangement, can therefore change the legal analysis. DWI's Regulation 8 guidance contains additional historic-authorisation caveats, so do not self-classify from a diagram alone.
Connecting more premises or materially changing occupancy can also affect average daily volume, sampling locations and the authority's monitoring programme. Use the supply category helper only as an orientation tool; the actual regulatory position belongs with the local authority.
Local-authority records and information
DWI's Regulation 14 note explains that the local authority's supply record includes core information such as source type, estimated population and volume, premises type and treatment details. It also includes a plan and description of the supply, the monitoring programme and sampling information. DWI says significant changes of circumstance should be noted as they happen.
The Regulations do not create a blanket operator duty to telephone the council every time a cartridge is changed. But the authority needs reliable information to discharge its own duties. DWI notes that, where necessary, an authority can use section 85 of the Water Industry Act 1991 to require a relevant person to provide information needed for its private-supply functions.
Practical rule: contact the authority early where you are proposing a new source, reinstating a disused source, changing domestic/commercial use, significantly redesigning treatment or distribution, connecting new premises, or making a change that could invalidate the existing risk picture or sampling plan.
What to record for each change
A useful entry should let someone who was not present reconstruct the decision. Record enough to connect the physical work to the risk assessment, schematic, maintenance plan and evidence file.
- Date the change was proposed, started and completed.
- Supply, site and exact asset or network section affected.
- Reason for the change: failure, planned upgrade, capacity, new use, authority action, contractor recommendation or other trigger.
- Before-state: model/specification, configuration, photographs and relevant drawing revision.
- After-state: new equipment, materials, settings, route, valves, tank, source or users served.
- Who designed, installed, inspected or authorised the work.
- Manufacturer instructions, commissioning sheet, service report, invoice or certificate where applicable.
- Any flushing, disinfection, verification, sampling or operational checks carried out.
- Whether the schematic, maintenance plan, emergency plan, sampling points or operating instructions changed.
- Whether the local authority or another competent professional was contacted, and what they advised.
Use stable asset names. “Changed filter” is weak evidence if the supply has five filters. “Replaced cartridge in PF-02, upstream of UV-01” can be tied to a schematic and maintenance history.
Examples of changes worth documenting
New or replacement treatment
Record new UV units, filters, softening or specialist media, dosing equipment, alarms and bypass arrangements. DWI's treatment guidance stresses that equipment should be suitable for the size and nature of the supply and that operating and maintenance instructions should be provided. For UV, record the model, validated operating limits where available, lamp/sleeve details and maximum design flow rather than assuming any replacement unit is equivalent.
Storage and distribution alterations
Record new or replacement storage tanks, pressure vessels, pumps, buried mains, branch extensions, isolation valves and dead-leg removals. DWI guidance highlights contamination risks during installation and repair of pipework and says storage and other parts of the supply can require disinfection before use.
Source changes
A new borehole, spring, well, abstraction point or source switch can materially change raw-water hazards and treatment needs. If the arrangement amounts to a new private supply or a reinstated supply after 12 months of non-use, DWI's Regulation 13 guidance applies.
Premises, use and demand
Record properties connected or disconnected, a change from private domestic use to letting or other commercial/public use, significant increases in occupancy, seasonal-use changes and new high-demand facilities. These changes can affect classification, estimated population/volume, representative sample points and treatment capacity.
Responsibility changes
Record a change in owner, operator, landlord, management company, contractor or other person responsible for critical parts of the supply. Capture handover of keys, manuals, alarm contacts, emergency arrangements and outstanding actions so knowledge is not lost even if the physical pipework has not changed.
Commissioning and recommissioning after alterations
Do not assume every alteration creates a “new supply” under Regulation 13. Replacing a treatment asset within an existing supply is normally a change to that supply, but it may still be significant enough for the local authority to review the risk assessment.
Where the work does create a new private supply, reinstates one after 12 months of non-use, or brings a previously abandoned/disused source into domestic use, DWI says the supply should not be put into domestic use until the local authority has completed the Regulation 6 risk assessment and determined the appropriate monitoring.
For ordinary infrastructure alterations, follow the competent installer's and manufacturer's commissioning instructions. DWI guidance says precautions are needed to avoid contamination during maintenance and installation. Its storage guidance says newly constructed storage and supply components may require disinfection before use. Keep the relevant commissioning, flushing, disinfection and verification evidence rather than reducing the entry to “works complete”.
Update the source-to-tap schematic
A change log and schematic should agree. DWI's examples-of-records guidance says accurate plans and schematics are important information for risk assessment. If a new branch, tank, UV unit or source is in the change log but not on the current schematic, the supply history is already drifting.
Use the private water supply schematic guide and keep superseded versions rather than overwriting them. A dated previous diagram can explain why an old sample location, valve number or treatment reference appears in historical documents.
Why chronology matters after an incident
When a sample fails, treatment stops, pressure is lost or contamination is suspected, the key question is often “what changed shortly before this?”. A dated alteration history can reveal a new connection, bypass, maintenance visit, source switch or storage change that would otherwise be missed.
Keep corrective actions separate from the change log. The corrective-action log should track the problem, assigned action and closure evidence; the change log should record the resulting alteration to the supply. Link the two records rather than duplicating them.
The same separation applies to the maintenance log: routine service activity belongs there, while significant configuration changes belong in the change history. This keeps search intent and operational records distinct instead of turning every page and every register into the same generic “keep records” message.
England and the other UK nations
This guide is written for England and refers to the Private Water Supplies (England) Regulations 2016 as amended. Do not reuse the Regulation numbers as if they applied throughout the UK. Wales has the Private Water Supplies (Wales) Regulations 2017; Scotland regulates relevant supplies under Scottish private-supply legislation including the 2017 Regulations; Northern Ireland uses the Private Water Supplies Regulations (Northern Ireland) 2017 and has a different regulatory structure. Check the applicable national regulator or local authority before applying this workflow outside England.
Frequently asked questions
Is a private water supply change log a legal requirement in England?
No specific provision in the Private Water Supplies (England) Regulations 2016 requires an owner or operator to maintain a document called a change log. Regulation 14 places the formal private-supply record duty on the local authority. DWI nevertheless recommends accurate operational records, maintenance diaries, schematics and plans because they support risk assessment and active management.
When should a private water supply risk assessment be reviewed after a change?
DWI's Regulation 6 guidance says the local authority should review a risk assessment whenever it considers the current assessment inadequate or circumstances have changed significantly, giving deterioration in raw-water quality and installation of a new treatment process as examples. The normal five-year cycle is therefore not a reason to ignore a material change.
Do I have to tell the local authority every time I replace a filter or UV lamp?
There is no general England-wide rule requiring the operator to notify the local authority of every routine consumable change. Keep maintenance records and follow the manufacturer's instructions. Contact the local authority where a change is material to the supply's risk, classification, monitoring, treatment arrangement, source, distribution or use, or where the authority has specifically required information.
Can a change in use alter whether the supply is Regulation 8 or Regulation 9?
Yes. Regulation 9 covers large supplies and water supplied as part of a commercial or public activity. Regulation 8 concerns certain onward distribution of water originally supplied by a water undertaker or licensed supplier. A new commercial use, new premises, a source change or a change in how mains water is distributed can therefore affect the regulatory position, which the local authority should determine for the actual arrangement.
What should I record when treatment equipment is replaced?
Record the old and new asset, reason for replacement, date, installer, model or specification, relevant flow and operating limits, commissioning or verification evidence, updated instructions, photographs and any consequential changes to the schematic, maintenance plan or sampling arrangement.
Does a new borehole or reinstated source need special handling?
Potentially. DWI's Regulation 13 guidance covers new private supplies, supplies reinstated after 12 months of non-use and previously abandoned or disused sources brought back into domestic use. It says such supplies should not be put into domestic use until the local authority has completed the required risk assessment and determined monitoring requirements.
How long should an operator keep change records?
The statutory 30-year retention duty in Regulation 14 applies to the local authority's private-supply records, not to an operator's own change log. For operational records, retain enough history to explain the current configuration and past incidents, and follow any specific local-authority, contractual, insurance or professional requirements that apply to your supply.
Related guidance and tools
- DWI — Regulation 6 risk assessment (England)
- DWI — Regulation 14 records (England)
- DWI — Regulation 13 new and reinstated supplies (England)
- DWI — Record keeping for owners and users
- DWI — Examples of records and schematics
- DWI — Regulation 9 large/commercial/public supplies
- DWI — Treatment guide
- DWI — Private supply legislation index
- legislation.gov.uk — Private Water Supplies (England) Regulations 2016
Regulatory statements here are England-specific. Confirm the position for your supply with the local authority or applicable national regulator before relying on a proposed change.