How do I know if my drain is collapsed or just blocked?

Frequency is the test. A one-off blockage that clears and stays clear was a blockage. Repeat blockages in the same place, slow decline over months, or ground sinking above the run point to structural damage.

Can a collapsed drain cause subsidence?

It can. Water escaping from a broken pipe washes fine material out of the ground, and where that happens under a foundation, settlement and cracking can follow. Drainage is a standard line of enquiry in subsidence claims.

Are rats a sign of a broken drain?

Frequently. Rats travel in sewers and get into gardens and cavities through breaks and open joints. A new rat problem is worth a camera survey rather than just bait.

Smells and repeat blockages should be investigated within weeks. Visible ground collapse, effluent surfacing, or new cracking in the building should be treated as immediate.

The warning signs of a collapsed drain

Repeat blockages in the same spot, drainage that gets slower over months, sinkholes or dips in a lawn or drive, persistent damp smells, rats indoors and new cracking near a drain run are the six symptoms that point to a collapsed or fractured pipe rather than an ordinary blockage.

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Blocked and broken are not the same problem

An ordinary blockage is an event: something goes down that should not, the drain backs up, it gets cleared, life continues. A collapsed drain is a condition, and it produces symptoms that keep coming back. Telling them apart matters because clearing a broken drain is money spent on a delay. These are the signs worth acting on.

The six signs

The same drain blocks again and again. The clearest signal of all. A sound pipe that gets blocked once tends to stay clear afterwards. A pipe that blocks every few months has something in it catching solids: a displaced joint, a fractured section, root, or a sag holding water.
Drainage that has been getting slower for months. Gradual deterioration rather than a sudden stop suggests the bore is narrowing, which is root ingress or a partial collapse rather than an obstruction.
A dip, soft spot or sinkhole in the ground. Where a pipe has broken, water escapes and washes fine material away, and the surface above eventually settles into it. A depression appearing over a known drain run is a serious sign.
Damp, sewage-like smells that will not go. A properly sealed system with working traps should not smell. Persistent odour in a yard, a cellar or a ground floor room means gas or effluent escaping somewhere it should not.
Rats indoors or in the garden. Rats live in sewers and get out through breaks. A sudden rat problem, especially in older terraced streets, is a classic indicator of a fractured drain nearby.
New cracking in walls or paths near a drain. Leaking drainage washes out the ground supporting foundations and slabs. Where fresh cracking appears close to a known run, drainage is one of the first things a surveyor will want ruled out.

What to do about it

Get a camera in the pipe. A CCTV survey at £100 to £250 converts a list of symptoms into a defect at a stated depth and distance, which is the only basis on which anyone should quote for repair. Do not accept an excavation quote from a firm that has not shown you footage of the defect, and do not keep paying for clearances on a drain that has now blocked three times. If the ground is visibly sinking, or cracking is appearing in the building, treat it as urgent and mention it when you request a quote.

What it usually costs to put right

Most faults that produce these symptoms turn out to be repairable from inside the pipe, with patch lining or relining at £300 to £1,000, so the word collapsed is often more alarming than the repair. A genuine collapse, or a run that has sagged badly, needs excavation and replacement, quoted per job. Before spending anything, check whether the damaged section is even yours, because the pipework beyond your boundary is the water company's, as the responsibility guide explains.