Drain mapping: what to ask for before you book

Start with the drainage search and drawings from your purchase, then ask your sewerage company which records it holds. Check that the plan covers the pipe you are interested in before paying for another service.

Yorkshire Water says its maps show the pipes it owns and has plotted, not private pipes or property connections. Thames Water also warns that some public sewers and lateral drains may be absent from its maps. An empty patch on a map is not proof that there is no drain there.

Sources: Yorkshire Water; Thames Water.

Choose the survey around the decision you need to make. If an architect, surveyor or water company will use the drawing, ask them to specify the information and format before you request quotes.

• Where does this pipe run? Ask about tracing and a drainage layout plan.
• What condition is it in? Ask about CCTV inspection and a written condition report.
• Will a drawing be suitable for planned building work? Send the recipient's requirements to the contractor.
• Do I only need existing public sewer records? Check the water company's records service first.

Sources: Metro Rod; Thames Water.

A mapping service can include pipe routes, access points, flow direction and recorded sizes and depths. Some services supply additional records or CAD files. These are items to agree in the quote, not things every contractor necessarily includes.

Ask for a distinction between locations actually traced or measured, routes inferred from records, and parts that could not be checked. If a depth or route matters to your building work, ask how it was established rather than treating a line on a drawing as a guarantee.

• The property and area covered, with recognisable reference points.
• Pipe runs and access points labelled so they match any photographs or CCTV report.
• Any foul and surface-water connections that the contractor has established.
• Recorded measurements and their limitations.
• The agreed file format, such as a PDF plan or a CAD file if your designer needs one.

Sources: Metro Rod.

The price depends on the area, access and detail required. Ask for a written total that separates mapping, camera inspection, any clearance and the files you need afterwards.

Do not compare a basic camera visit with a measured site plan as if they were the same job. Our cost guide shows named firms' published survey and mapping examples, with coverage and VAT conditions. They are not a national mapping average.

Sources: Metro Rod.

Send the contractor your existing plan, the area you want checked and the reason for the work. Tell them about inaccessible covers and arrange the property owner's permission if you are buying the house.

For building work, the person designing or approving the work should decide whether the proposed plan is sufficient. This guide cannot confirm safe excavation positions or grant permission to build.

Sources: Thames Water.

• Does the price include tracing as well as camera inspection?
• Which pipes and access points will you cover?
• How will you distinguish measured routes from assumed ones?
• Will depths, flow direction and pipe sizes be recorded where established?
• Which drawing and video files will I receive?
• What will you charge if access or a blockage prevents completion?
• What is the total including VAT, and when will I receive the plan?

Find and check a drainage contractor when you are ready to ask for quotes.