CCTV drainage surveys
Sewer Maps
A public sewer map shows the assets a water company records in its area, but it is not a complete picture of every pipe serving a property. Records can be incomplete or may not show every connection. We can help with mapping surveys that record accessible drainage on site.
What a public sewer map shows
A public sewer map is the record a sewerage undertaker keeps of the public sewers and lateral drains it is responsible for. Under section 199 of the Water Industry Act 1991, undertakers in England and Wales must keep specified sewer records and make the map available for public inspection free of charge at reasonable times. The information shown varies by undertaker and by the records available. It does not normally provide a complete map of private drainage within a property, and it may not show every connection.
Records may include historic plans, adoption information and as-built drawings. They are records of known assets rather than a measured site survey, so the mapped position should be checked on site where location matters. Depth information may also be limited or absent. A sewer map is a useful starting point, but it is not a substitute for locating drainage on site.
Free inspection and paid searches
Water companies provide a free inspection of their public sewer records, usually by appointment at their offices or through an online request. This is a statutory right under section 199. For a formal written response, many companies offer a paid asset location search or a developer enquiry. The paid product usually includes a plan extract and a written summary of assets near a site.
For property transactions, a CON29DW drainage and water enquiry is commonly used during conveyancing. It reports information held by the relevant water and sewerage companies, including specified questions about water and sewer connections and recorded public sewer assets. Because it relies on the providers’ records, it does not replace an on-site drainage survey.
Why records are incomplete after 2011
On 1 October 2011, most qualifying private sewers and lateral drains connected to the public network in England and Wales transferred to the regulated sewerage companies. The transfer did not mean that every asset was immediately mapped. Where the location or particulars of an older asset were not known or reasonably discoverable, the statutory records can still have limitations.
Section 199 applies in England and Wales. For properties in Scotland or Northern Ireland, use the relevant water authority’s current record-search process.
What a mapping survey adds
A drain mapping survey records the accessible drainage layout found on site. Depending on the agreed scope, it can combine CCTV inspection, access-chamber checks, tracing and measurement. The resulting plan can record pipe routes, connections, observed sizes and other details that can be established during the survey. This is useful when public records are unclear or when a project needs a better site record of the drainage layout.
We can help with drain mapping and connectivity surveys for domestic, commercial and adoption projects. The output depends on access, the number of manholes and the level of detail agreed before work starts. A mapping survey shows what is visible and accessible on the day. It cannot prove the absence of a pipe that is buried, unchambered or outside the surveyed area.
Build-over and adoption projects
If you plan to build near or over a public sewer, the relevant sewerage company may require approval before work starts. Its current application requirements will determine what plans, records or survey information are needed. A build-over checker can help you prepare questions for the water company, but it does not grant permission. Only the relevant authority or sewerage company can give the required approval.
For new developments, a section 104 agreement can set the requirements for sewers intended for adoption. Drain mapping during or after construction can help record the as-built drainage layout where that information is required. See our Section 104 adoption CCTV survey page for more on that process.
Water company record searches
The table below gives examples of water and sewerage companies and the service area to look for when starting a record search. Requirements vary, so confirm the current process directly with the relevant provider before relying on a map for a design or legal decision.
| Company | Nation | Record search starting point |
|---|---|---|
| Thames Water | England | Developer services and asset location searches |
| Severn Trent | England | Developer services and property searches |
| United Utilities | England | Developer services and asset records |
| Anglian Water | England | Developer services and asset location |
| Yorkshire Water | England | Developer services and records |
| Scottish Water | Scotland | Developer services and asset records |
| NI Water | Northern Ireland | Developer services and records |
For build-over enquiries, our Thames Water build over agreement and Severn Trent build over agreement pages cover two of the larger companies. The build over agreement checker helps you prepare questions, but it is not a regulatory certification.
Limits and practical decisions
A sewer map is a record, not a survey. It can be wrong, incomplete or out of date. Before relying on one for a build-over application, a conveyance or a repair, consider what the map does not show. A CCTV and mapping survey can fill some of those gaps by recording what is present and accessible. It cannot see through deposits, detect every defect or confirm the condition of a pipe it cannot reach.
If you need to know where a pipe runs, what it connects to and how deep it is, a mapping survey is usually the practical next step. If you only need the water company’s recorded position, a record search may be enough. The two are often used together. For a broader view of drainage investigation, see our drainage survey page.
Free online tool
Build Over Agreement Checker
Check what to ask your sewerage company before building near a drain or sewer.
Common questions
Frequently asked questions
Is a public sewer map the same as a drain map?
No. A public sewer map shows the assets the water company records as public. A drain map records the drainage layout on a property, including private drains and connections. The two can be compared, but they are produced for different purposes.
Can I get a sewer map for free?
Under section 199 of the Water Industry Act 1991, sewerage undertakers in England and Wales must make the statutory sewer map available for public inspection free of charge at reasonable times. Providers may also offer paid searches or other record products, so check the current process with the relevant company.
Why is my property not shown on the sewer map?
The record may be incomplete or may not show a connection in the position you expect. The 2011 transfer brought most qualifying private sewers and lateral drains in England and Wales into water company ownership, but it did not make every asset immediately identifiable on a map. A mapping survey can record accessible drainage on site, but it cannot prove that an untraced pipe does not exist.
Does a sewer map show private drains?
Generally no. Public sewer maps focus on public sewers and lateral drains. Private drains within a property boundary are usually not shown. A drainage survey is needed to record those.
Can a sewer map be used for a build-over agreement?
It is often requested as part of a build-over application, but it does not grant permission. The water company decides whether to approve the build-over. A build-over checker can help you prepare questions, but it is not a regulatory certification.
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