Revealed: 7 Signs of a Collapsed Drain | Warning Signals

Close-up inside a collapsed drain pipe filled with jagged rubble and muddy sediment.

Most people never give their drains a second thought until something goes wrong. A blocked sink or a smelly manhole is annoying, sure. But a collapsed drain? That’s a whole different beast.
It’s the kind of hidden problem that quietly eats away at your home’s health, right beneath your feet. And because it’s out of sight, many homeowners in Plymouth, Devon, and Cornwall don’t notice it until the damage is already well underway.

That’s why it pays to know the early warning signs. Catch it early and the fix is often straightforward. Ignore it, and you could be looking at damp walls, garden sinkholes, or even structural damage.
Let’s walk through the key signs of a collapsed drain and what to do if you spot them.

What Exactly Is a Collapsed Drain?

In plain terms, it’s a section of pipe that has broken, cracked, or caved in to the point where it can’t carry waste and water effectively anymore. The result? Backups, leaks, and sometimes full system failure.
Unlike surface clogs, collapsed drains tend to be buried deeper. That makes them trickier to diagnose without the right tools. But with a bit of know-how and a watchful eye, the warning signs aren’t hard to spot.

1. Persistent Bad Smells

Unpleasant odours that linger even after cleaning the kitchen or bathroom are a red flag. The smell might be coming from inside the walls or beneath your feet. If waste is getting trapped behind a damaged section of pipe, it starts to rot. That smell will work its way up through plugholes, outdoor grates, or even through your floorboards.
You might notice it most after running taps or flushing the toilet. In many cases, the odour is strongest near inspection chambers or outdoor drains.
If it still smells after a clean, that’s when you need a professional to check deeper.

2. Slow or Sluggish Drainage

A slow drain isn’t unusual, but if you’ve already tried the usual tricks like plunging or using a drain snake and water is still taking its time to disappear, it’s time to consider the bigger picture.
Slow drainage across multiple plugholes suggests a blockage further down, often beyond the reach of DIY tools. If water is backing up in the bath when you flush the toilet or the kitchen sink gurgles after a shower, these cross-signals could mean a collapsed drain is disrupting the whole flow.

3. Sunken Ground or Garden Dips

This one often goes unnoticed, especially in gardens or along older driveways. If a section of the ground starts to sink or form a dip, check it out. A collapsed pipe below may be leaking water and waste into the surrounding soil, slowly washing it away.

Over time, this can cause voids to form underground and eventually the surface gives in. If you spot soft patches of lawn or sagging paving stones, don’t just fill it in.

Get it checked before it turns into something much bigger.

4.

Rising Damp or Unexplained Water Stains

Water from a damaged drain doesn’t always stay hidden. If it seeps into the soil beneath your home, that moisture will eventually start rising. Damp patches on ground-floor walls, peeling paint, black mould, or a persistent musty smell can all point to hidden water damage.

This is especially common in older properties across Devon and Cornwall, where clay pipes are still in place and waterproofing may be less robust.

If you’ve ruled out internal plumbing leaks, look to your drains as the next likely cause.

5. Recurring Blockages in the Same Place

It’s frustrating when a drain keeps blocking, no matter how often you clear it. This is often a sign that something more serious is lurking in the system. A cracked or collapsed section of pipe will collect debris over and over again, and standard clearing methods won’t touch the real issue.

The blockage might seem fixed one day, only to come back days or weeks later. That’s your clue. It’s time for a CCTV drain survey, which can reveal structural damage without the need for digging.

At Drainblock Services, we use specialist cameras that thread through your drainage system and show us exactly what’s going on in real time.

6. Cracks in Walls or Around External Brickwork

This one surprises a lot of people. If a pipe is leaking underground near your home’s foundation, the shifting soil can stress the structure. Over time, that pressure can lead to cracks, especially in older properties with less flexible materials.

Small cracks around windows, doors, or in garden walls can be the first sign. Keep an eye on them. If they grow, or new ones appear, get them investigated.

7. Increased Pest Activity

Rodents love a broken drain. Rats, in particular, often travel through drainage systems and if a pipe is cracked or collapsed, it can give them direct access to your garden or even your home.

Scratching in the walls? Droppings in the shed? More pest activity than usual? Don’t just lay traps. Investigate the root cause because your drains might be giving them a free pass.

What Causes Drains to Collapse?

It’s not always one dramatic event. Often, it’s a mix of age, weather, and wear. Some of the most common causes include:

• Tree root intrusion: Roots push through joints and grow inside, eventually cracking the pipe

• Soil movement: Particularly after heavy rain or drought, shifts in soil can crack underground pipes

• Poor installation: Pipes that weren’t laid correctly in the first place are more likely to fail

• Old materials: Many homes in Plymouth and the surrounding areas still use clay pipes and these weaken over time

• Heavy surface pressure: Cars parked over shallow drains or new construction work can damage pipes beneath

Interior view of a drain pipe captured by a CCTV camera, showing rough pipe walls, a camera head in view.

How We Identify a Collapse Without Guessing

At Drainblock Services, we don’t do guesswork. We use CCTV drain inspections to get eyes underground without touching your garden. Our equipment records crystal-clear footage, so we can show you exactly what’s causing the issue.
From there, we advise on the right fix whether that’s patch lining, full drain relining, or a more complex excavation if the damage is too severe to repair from within.

Contact Us

Repairs That Don’t Destroy Your Garden

The thought of a major dig-up job puts people off. But in most cases, it isn’t needed. We use trenchless methods wherever possible, which means minimal mess and disruption.
Depending on what we find, your repair might be done in a day with no torn-up lawn or driveway slabs to worry about.

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Partially removed wooden deck panels revealing the joists, exposed ground, and a blue hose alongside hand tools.