Collapsed Drain? Signs, Causes and Repair Options

Drains under London homes are often older than anyone living above them. Many Victorian and Edwardian streets still run on salt-glazed clay pipes laid in short lengths with mortar joints, and a century of tree roots, traffic, subsidence and clay soil that swells and shrinks with the seasons eventually finds the weak joint. When a section cracks, slips or caves in, the drain stops being a pipe and becomes a channel through the soil.

If waste water is coming back into the house now, stop using water and follow our guide to sewage backing up into the house first. The cause can be found once the water is moving again.

Seven signs a drain may be broken

1. The same blockage keeps returning, a few weeks after it was cleared, in the same chamber.
2. Paving, a lawn or a path dips in a line running away from the house.
3. Rats in the garden, under the kitchen floor or in a wall cavity. Broken drains are a favourite route into a building.
4. A damp patch low on an inside wall, or on a cellar floor, that no pipe above explains.
5. A sewage smell outside when nothing is blocked.
6. Cracks in a wall near where the drain runs, from washed-out soil under the foundation.
7. Slow drainage everywhere at once, rather than at one sink or toilet.

One sign on its own is not proof. Two or three together usually justify a camera.

How it is confirmed: the camera survey

A waterproof camera on a push rod is fed into the drain from an inspection chamber. It records the inside of the pipe on video, with a distance counter, so the report shows exactly how far along the run a crack, root ingress, displaced joint or collapse sits, and roughly how deep. That turns a guess into a plan, and it is also what an insurer, a buyer’s surveyor or the water company will want to see. Our CCTV drain survey page explains what the footage and report contain.

The repair options

Patch lining. A short sleeve of resin-soaked fibreglass is pulled into place on an inflatable packer and cured against the pipe wall. Good for a single crack or open joint.

Full lining. A longer liner runs the length of a damaged section, forming a new pipe inside the old one. Suited to a run with several cracks and roots, as long as the pipe has not lost its shape.

Excavation and replacement. Where a section has crushed, dropped or vanished, the ground is opened at that point and the broken length replaced with modern plastic pipe and flexible couplings. Ground is reinstated afterwards, though matched paving may take a second visit.

Root cutting first. Where roots have pushed through joints, a cutter on the jetting hose clears them before any lining goes in.

The camera footage decides which one; we will show you it and talk you through it before any work is booked. Lining and excavation are charged at the same hourly rate as everything else, and you are told what each step is as it happens.

Who owns the broken bit

Since 2011, most shared drains and lateral pipes outside a property’s boundary in England have been the water company’s responsibility, while a pipe serving only your home, within your boundary, is yours. The survey report shows where the damage is, which usually settles who pays. Our guide on blocked outside drains covers what to check in the chamber before you ring anyone.

Why waiting costs more

A small crack lets water out into the soil and lets roots in. Water washes fine soil away from under the pipe, which then sags, which catches more debris. A crack that could be lined in an afternoon this autumn can become a dig and a garden wall to rebuild by spring. If you have had two blockages in a year, book a survey: call or WhatsApp 07861 933265.