Drain keeps blocking? What to ask before another clearance

Record the dates, affected fittings, any overflow and what the last contractor did. Note whether the problem returns after days, weeks or months. Keep the previous invoice and any photographs or report.

That record helps you request a different answer from the next visit. Instead of simply ordering another unblock, explain that you want to understand the recurring fault and the evidence needed to choose the next step.

Sources: DASA.

DASA describes camera inspection as a way to investigate repeated blockages and identify issues such as roots, displaced joints or damaged pipework. Those are possible findings, not conclusions you can draw from a slow sink.

Ask the contractor to explain what it can inspect and what may be hidden by water or debris. A recommendation should distinguish what was seen from what is suspected. If a camera cannot pass, ask how the cause will be confirmed.

Sources: DASA.

A heavily obstructed pipe can prevent a useful camera view. Agree whether the quote includes any necessary cleaning, what it costs and whether another inspection is needed afterwards.

For a hypothetical booking, “clear the drain” and “clear it, inspect the affected run and supply a report” are different scopes. Write the second request out if that is what you need. Do not assume an emergency clearance includes footage you can use later.

Sources: DASA.

If neighbours are affected or you suspect the blockage is in public pipework, contact the sewerage company. Thames Water’s guidance distinguishes private drains from blockages in sections it maintains.

Report sewage escaping through the provider’s official channel rather than waiting for a routine comparison of survey prices. Explain where it is appearing. Do not enter a chamber or put yourself in contact with sewage to collect evidence.

Sources: Thames Water.

Ask what the new work is expected to achieve that the previous clearance did not. Is it another clearance, a condition survey, a local repair or a longer treatment? Request the location and reason for any proposed repair.

Keep a simple list of known costs and missing items. Ask for the full total including VAT, and get approval arrangements for extras in writing. A contractor promising a permanent cure should explain the evidence and the written terms behind that promise.

Sources: OneFlow.

Thames Water advises keeping fats and inappropriate waste out of drains and flushing only suitable material. Ask the contractor whether it actually found a build-up or whether a pipe defect needs separate attention.

Changing household habits may be sensible, but it should not replace an explanation of a defect shown on camera. Equally, the presence of a nearby tree is not proof that roots are responsible: ask to see the finding.

Sources: Thames Water; DASA.

• What did the last clearance establish?
• Which pipe run should be inspected now?
• Is cleaning needed first and is it included?
• What evidence supports the proposed cause?
• Is any shared or public pipework involved?
• Which parts could not be inspected?
• What will the next job do differently, and what is its VAT-inclusive total?

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