Signs of a Collapsed Drain (and How to Tell It From a Blockage)
Written by the Urgent Drainage Solutions teamPublished Updated 6 min read
Quick answer
The main signs of a collapsed drain are blockages that return soon after clearing, a sewage smell outside, sunken or damp ground over the drain, damp patches on walls near it, an inspection chamber that keeps filling, and rats. Only a CCTV survey confirms a collapse. MyJobQuote puts a typical collapsed drain repair at about £850.
- A blockage that keeps coming back within weeks of clearing is the most common sign of a damaged or collapsed drain.
- Sunken ground, damp walls, outside sewage smells and rats point to a leaking or broken pipe rather than a simple blockage.
- Only a CCTV drain survey can confirm a collapse and show where it is and how long it is.
- MyJobQuote puts a typical collapsed drain repair at about £850, and a full collapse at £1,000 to £3,000 or more.
- Our drain repairs start from £250 + VAT, quoted from the survey footage, with a 12-month workmanship guarantee.
The signs of a collapsed drain are blockages that return soon after clearing, a sewage smell outside, sunken or damp ground over the drain run, damp patches on walls near it, an inspection chamber that keeps filling with water, and rats around the house. A simple blockage causes slow draining and gurgling but not damage to the ground or walls. Only a CCTV drain survey can confirm a collapse, and our drain repairs start from £250 + VAT once the damage has been found and measured.
This guide lists the warning signs, shows how to tell a blockage from structural damage, sets out the safe first steps and explains how a collapsed drain is repaired. For prices, see our collapsed drain repair cost guide.
What are the signs of a collapsed drain?
A collapsed or badly damaged drain catches waste and leaks into the ground, so the signs appear both inside and outside the house. These are the ones drainage engineers look for:
- Blockages that keep coming back. A drain that needs clearing again within weeks usually has a broken section or displaced joint holding debris.
- A sewage smell outside with no obvious overflow, often near a gully, chamber or the line of the drain.
- Sunken, soft or unusually damp ground above the drain run, or paving that has dropped.
- Damp patches or mould on internal walls near where the drain passes.
- An inspection chamber that fills with water. If the chamber is full, the pipe downstream is blocked or broken.
- Several fittings slow at once, such as toilets, sinks and showers, especially downstairs.
- Rats in the garden or house, since rats use broken pipes to move between sewers and buildings. See our guide to rats in drains.
- New cracks in walls or paving near a drain, which can mean soil is being washed away.
None of these alone proves the pipe has collapsed, but two or more together, or any sign outside the house, should be checked with a camera.
How can you tell a blocked drain from a collapsed one?
Look at where the symptoms are and how quickly they return. A blockage is inside the pipe; a collapse also shows up in the ground and the structure around it. This checklist is a guide, not a diagnosis:
| What you notice | More likely a blockage | More likely damage or collapse |
|---|---|---|
| One slow sink, bath or shower | Yes | Rarely |
| Several fittings slow at once | Yes, in the main drain | Possibly |
| Problem returns within weeks of clearing | Possibly | Yes |
| Gurgling from plugholes or the toilet | Yes | Sometimes |
| Sewage smell outside with no overflow | Sometimes | Yes |
| Sunken, soft or damp ground over the drain | No | Yes |
| Damp patches on internal walls near a drain | No | Yes |
| Rats around the house or garden | Sometimes | Yes |
| House built between the 1950s and 1970s with original drains | No | Higher risk (pitch fibre) |
Blockages and damage often go together. A displaced joint catches wipes and fat, and a long-standing blockage puts pressure on weak joints. Clearing a blockage without looking at the pipe can hide the real cause.
What causes a drain to collapse?
Most collapses follow years of smaller defects. The common causes are:
- Age and ground movement. Joints in older clay drains can open or displace, and cracks grow.
- Tree roots entering through open joints and cracks, then expanding. See tree roots in drains.
- Pitch fibre pipes. The Financial Ombudsman Service describes pitch fibre as wood cellulose impregnated with tar, popular between the 1950s and 1970s. It deforms under load and can blister. Read our guide to pitch fibre pipes.
- Load from above, such as a new driveway, heavy vehicles or a structure built over the pipe.
- Poor original installation, such as inadequate bedding or a backfall where water sits.
- Repeated blockages that let water build up and leak through weak joints.
What should you do if you think your drain has collapsed?
Stop using it where you can, avoid digging, and get it surveyed. These first steps are safe for a homeowner:
- Cut water use into the affected drain. Every flush adds to the backlog and the leak.
- Ask your neighbours whether they have problems too. If they do, the fault may be in a shared pipe or public sewer.
- Look, don't dig. Wearing gloves, you can lift a light gully grate to see whether it's full. Don't lift heavy or stuck covers, and keep children and pets away from open chambers.
- Don't pour drain chemicals into a drain you suspect is broken. They won't fix a structural fault, and different products must never be mixed.
- Treat any overflow as contaminated. Keep skin contact to a minimum and wash hands thoroughly.
- Tell your insurer early. The Financial Ombudsman Service says you should contact your insurer before repairs; if you can't, keep photos, a detailed report and an itemised invoice.
If sewage is coming into your home now, see our emergency drainage page.
Who is responsible for a collapsed drain?
It depends where the collapse is. Severn Trent's sewer responsibility guide says the water company is responsible for pipes shared with neighbours and pipes outside the property boundary that connect to its network, while homeowners are responsible for pipes within their boundary that serve only their house. In a terrace, much of the drainage behind the houses may be a shared public sewer. A survey shows exactly where the damage sits. See who is responsible for blocked drains.
How much does a collapsed drain repair cost?
A typical collapsed drain repair costs about £850 according to MyJobQuote's drain repair guide (updated 27 August 2026), from a few hundred pounds for a patch repair to £1,000–£3,000 or more for a fully collapsed pipe. Depth, what sits on top of the pipe and whether it can be relined or must be dug out decide most of the bill. Our collapsed drain repair cost guide sets out the full price ranges, the cost drivers and who pays.
Our drain repairs start from £250 + VAT for a simple repair. Every repair is based on a CCTV survey, quoted before work starts and covered by our 12-month workmanship guarantee. We also carry out drain repairs in Derby and drain repairs in Leicester.
How is a collapsed drain repaired?
The survey decides the method. A camera shows the type of damage, where it is, how long it is and whether the pipe still holds its shape:
- Patch repair for a single crack, open joint or root entry point in an otherwise sound pipe.
- Relining, where a resin liner cures into a new pipe inside the old one, for defects spread along a run that still holds its shape. See our drain relining service.
- Excavation and replacement where the pipe has collapsed, is badly deformed or sits at the wrong fall.
Our guide to drain relining vs excavation compares the three. If you plan to claim on insurance, WRc's Drain Repair Book, which it says "is widely used by both insurers and drain repairers", is the reference many insurers and contractors work from.
When to call a professional
Call a drainage engineer if a blockage doesn't clear with basic steps, keeps coming back, or comes with any of the outside signs above: smells, sunken ground, damp walls or rats. We carry out CCTV drain surveys from £149 + VAT and drain repairs from £250 + VAT across Nottingham, Nottinghamshire, Derbyshire, Leicestershire and Lincolnshire, and we agree the price before any work starts.
Our engineers work 7 days a week from 6am to 8pm, with emergency call-outs 365 days a year. Call 07300 600 950 or book online.
Sources
Frequently Asked Questions
Cite this guide: “Signs of a Collapsed Drain (and How to Tell It From a Blockage)”, Urgent Drainage Solutions, 2 October 2026. https://urgentdrainagesolutions.co.uk/blog/signs-of-a-blocked-or-collapsed-drain
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