Signs of a collapsed drain — and what to do about it

A collapsed drain is a section of underground pipework that has partially or completely failed structurally — the pipe has cracked, deformed, offset or fallen inwards. Water still flows, but restricted, and debris quickly forms blockages at the failure point.

Most collapses are age-related failures of Victorian clay drainage, but ground movement, poorly-installed extensions and heavy vehicle traffic over shallow drains can all cause new collapses.

Look for sinkage or dips in the ground above known drain runs — even a subtle depression can signal loss of pipe support underneath. Wet patches in the garden with no obvious cause, unusual growth in vegetation directly over a drain run, and rat activity near the property are all classic surface indicators.

Recurring blockages every few weeks or months, especially cleared and then coming back, are a strong indicator of a structural fault rather than a one-off clog. Slow drainage in ground-floor fixtures after heavy rain suggests the drain is running near capacity because of internal restriction.

An HD CCTV camera pushed through the drain will show cracks, open joints, offset joints, bellied sections and full collapses in high detail. The engineer grades every defect against the WRc standard and produces a report you can use to guide repair decisions and support insurance claims.

For localised defects, a patch liner is often enough — a resin-impregnated sleeve installed inside the pipe over the fault, curing in place. For widespread damage across a run, a full-length CIPP liner installs a complete new pipe inside the old one.

Only when the pipe is fully collapsed or deformed beyond lining is excavation and re-lay needed. A good drainage contractor will always try lining first — it's cheaper, faster and less disruptive.