Drain survey after flooding: decide what needs investigating

GOV.UK directs reports about blocked sewers to the local water company, public drains and flooded roads to the council, and main-river or sea flooding to the Environment Agency. The right contact depends on the source. Do not decide who owns a pipe simply from where water appeared in your garden.

This is a follow-up booking guide, not emergency or clean-up instructions. Follow your water company's flood advice and do not enter floodwater or chambers to gather evidence. Thames Water advises avoiding affected areas and taking photographs only when safe. Outside England, use the local national and water-company reporting arrangements instead of copying this contact route.

Sources: GOV.UK; Thames Water.

A visit after the water has gone is not the same as seeing the event unfold. Thames Water specifically asks for safe photographs because water levels can fall before its engineers arrive. Record when the flooding was first noticed, the places affected and the reference given when you reported it.

Keep your observations separate from explanations suggested by other people. Write that water emerged near a cover if that is what you saw; do not turn that observation into a confirmed cause. Include previous incident dates, any clearance work and who attended. Give this chronology to the person coordinating the investigation, without posting private household details publicly.

• Keep original photographs with their dates.
• Record the company incident reference and any written findings.
• Note which questions were still open after the first response.

Sources: Thames Water.

Thames Water lists heavy rainfall and pipe blockages among sewer-flooding causes. Finding a visible defect later does not, by itself, establish its role in the earlier incident. Ask the investigator to explain how the proposed inspection relates to the evidence from the event and whether other information is needed.

A useful brief names the pipe lengths to inspect and the question for each length. Ask whether the visit concerns a suspected obstruction, a condition assessment or tracing the affected connection. If the unanswered question concerns the wider network or rainfall response, ask who can assess that. Do not buy a whole-property guarantee under the name of a camera survey.

Sources: Thames Water; GOV.UK.

Before commissioning a private inspection, ask the water company whether it has an investigation in progress and what findings it will provide. Where an insurer is involved, ask what evidence it needs and whether it wants to authorise or arrange a visit. Do not assume privately ordered work will be reimbursed.

Keep cleaning, emergency attendance, CCTV inspection and later repair proposals as separate lines in your records. Ask what was done on each visit and what remains unresolved. Thames Water notes that further work can require cleaning, specialist equipment or waiting for water levels to fall; that is its response guidance, not a timetable for every company.

Sources: Thames Water.

Request a plan, the inspected lengths and an explicit account of any sections that could not be assessed. Ask the report writer to separate observed condition from their explanation of the flood. Where a repair is suggested, ask what evidence connects that repair to the problem being investigated and who should approve the next step.

Do not treat a clean-looking recording as a certificate that flooding cannot happen again. Keep the incident log alongside the inspection report so that the next professional sees both. If the original explanation remains uncertain, record that honestly and ask who is taking responsibility for resolving the remaining question.

Sources: Thames Water; Thames Water.

• Has the incident been reported through the correct local route?
• What incident evidence is available without entering an unsafe area?
• What question will each surveyed pipe length answer?
• Is a company or insurer already arranging an investigation?
• Which work and report outputs are included in the quote?
• Who will interpret the findings alongside the flood history?

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