Drainage guide

Why does my drain keep blocking?

Q: Why does my drain keep blocking?

Recurring blockages usually mean a structural fault — roots, a displaced joint or a partial collapse. A CCTV survey pinpoints the cause so it’s fixed once.

Reviewed by the Drainage Quotes team Last updated 7 July 2026

Open drain gully with tree roots and debris partially blocking the pipe

Recurring blockages usually mean a structural fault — root ingress, a displaced joint or a partial collapse — not just debris. Wet wipes and fat cause around 93% of the 300,000 sewer blockages recorded in the UK each year (Water UK), but a drain that blocks repeatedly needs a CCTV survey to find the underlying cause.

What are the most common causes?

One-off blockages are usually debris, wipes or fat. Repeat blockages in the same spot point to a fixed defect — tree roots, a displaced or cracked joint, a bellied pipe that holds water, or a partial collapse — that keeps catching everything that passes.

Wipes and fat: the 93% problem

Wipes made up around 93% of the material causing the sewer blockages Water UK investigated, with less than 1% being genuinely flushable product. Fat, oil and grease contribute to over 20,000 Thames Water blockages a year — more than a quarter of incidents (Water UK / Thames Water).

When is it tree roots?

Roots seek out the moisture in drains and push through the smallest crack or joint, then grow into a mat that traps debris. If blockages return every few months, especially near trees or hedges, root ingress is a common cause — confirmed and cut back after a CCTV survey.

When is it a collapse?

A partial collapse or a bellied section leaves a permanent low point where waste settles and blocks. No amount of rodding fixes it — the pipe itself has failed, and the section needs relining or, if fully collapsed, excavation.

How does a CCTV survey pinpoint the cause?

A camera sent through the drain shows the exact location and nature of the fault — roots, joint, belly or collapse — with a recorded report and location plan. That turns a recurring problem into a single, targeted repair rather than repeat call-outs.

UK drainage in numbers