Collapsed Drain Repair Without the Guesswork

Signs of a collapsed drain

A collapsed drain is a pipe that has broken through and caved in, or been crushed out of shape, so waste can no longer pass freely. The early signs are easy to mistake for an ordinary blockage:

• a blockage that comes back within days or weeks, always at the same point
• slow drains and gurgling across the whole house, not just at one sink
• a sewage smell outside, or damp low down on a wall near the drain run
• a dip, a hole or sinking paving along the line of the drain
• rats in the garden or indoors
• a patch of lawn that stays soggy or grows greener than the rest

One sign on its own proves very little. Several together, especially repeat blockages plus ground movement, are worth a camera survey. Our guide to the signs of a collapsed drain goes through each one and what else could cause it.

What causes drains to collapse

• Age and pipe material. Older clay drains have joints at short intervals, and every joint can crack or shift. Pitch fibre pipe, fitted to many post-war homes, softens and flattens under load.
• Tree roots. Roots get in at a joint, then thicken until the pipe splits.
• Ground washing away. When a pipe leaks, water carries soil away from around it until the pipe has nothing underneath and breaks. Approved Document H names fine sands and silty soils as easily eroded by leaking drains, and much of Bournemouth and Poole is built on sandy ground (British Geological Survey).
• Clay that moves. Clay soils shrink in dry summers and swell in wet winters, working joints apart year after year.
• Weight on top. A shallow pipe that coped under a lawn can crack under a new driveway, a parked van or a delivery lorry.
• Building work. Footings, fence posts and old excavations often sit close to drain runs and can damage them.

How we repair a collapsed drain

Relining or digging?

A broken drain pipe repair doesn't always mean a trench. If the pipe is cracked or partly broken but still round, it can usually be lined from inside, which is quicker and keeps the ground intact. Our drain relining page explains how. A section that has fully caved in can't be lined, because there's nothing left for the liner to form around. That section has to be dug out and replaced.

Collapsed drains under driveways, extensions and houses

Under a driveway

Block paving is lifted and stacked so it can be relaid. Concrete and tarmac are cut along a neat line, broken out and replaced. Reinstating a drive adds time and cost, and new concrete won't be an exact colour match to old.

Under an extension or conservatory

The first question is whose pipe it is. If it carries waste from more than one property, it is likely to be a public sewer, and Approved Document H is clear that repair or replacement of a public sewer is carried out by the sewerage undertaker (the water company). Many extensions were built over drains under a build over agreement, so check your paperwork. If the pipe is yours alone, we either line it from the manholes on each side or lay a new route around the extension and seal the old one off.

Collapsed drain under the house

Digging through a floor is the last resort. A pipe under a house is usually relined, or bypassed with a new run outside the walls. A new route is new drainage work under the Building Regulations, so we'll tell you before we start whether Building Control needs to be involved.

What collapsed drain repair costs

Collapsed drain insurance claims

Many buildings insurance policies cover accidental damage to the underground pipes that serve your home. Many also exclude wear and tear and gradual deterioration, and every insurer words it differently. Read your policy, or ring your insurer, before any digging starts: some want to approve the quote first, and some send their own contractor.

What insurers usually ask for:

• CCTV footage showing the damage
• A written report giving the location, the type of damage and the likely cause
• Photos of any damage above ground, such as sunken paving or cracked walls
• An itemised repair quote

We can supply all four. The report describes what the camera shows, plainly and honestly. If roots or ground movement did the damage, it says so. If the pipe has simply worn out, it says that too, because an insurer's own surveyor will check.

What collapsed drain repair can and can't fix

• We repair private drains. If the collapse is on a shared sewer, or on the stretch of your drain outside your boundary, the water company normally fixes it (Wessex Water or Southern Water, depending on where you live). We'll give you the footage to send them. Our guide on who is responsible for blocked drains explains the split.
• A drain repair stops the leak, not the damage it caused. Cracked walls or a sinking floor need your insurer and a structural engineer.
• Relining can't fix a pipe that has fully caved in, so we won't sell it for one.
• Paving can go back as it was, but poured surfaces can't. New concrete or tarmac will look newer than what's around it.

Not sure the drain has collapsed at all? The wider options are on our drain repairs page.

Recent collapsed drain jobs

Collapsed drains our engineers have found and fixed recently, with stills from the camera.

Our guarantee on collapsed drain repairs

Every section we replace or line comes with our 10-year guarantee on relining and repairs. The footage we take before backfilling shows the new pipe as we left it, which also helps if you sell the house. Details are on our guarantee page.

Areas we cover for collapsed drains

Engineers based in Bournemouth, Poole and Christchurch repair collapsed drains for homes across Dorset and Hampshire.

Collapsed drain FAQs