A cracked drain pipe is usually caused by tree roots, ground movement, age or heavy loads above the pipe. Warning signs include drains that keep blocking, bad smells, damp patches, sunken paving and rats. A CCTV survey confirms the damage, and most cracks can be fixed by no-dig drain lining rather than excavation.
Drain pipes are out of sight, which means a crack can sit there quietly for years, leaking waste water into the ground, letting roots in and slowly getting worse, until it announces itself as a blockage that will not stay cleared or a damp patch nobody can explain. This guide covers what actually cracks drain pipes, the signs to watch for above ground, how a suspected fault gets confirmed, and the realistic repair options, most of which no longer involve digging up your garden.
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What causes a drain pipe to crack
Drains fail for a handful of predictable reasons, and around Cornwall and Devon we see the same culprits again and again.
Tree and shrub roots
Roots are the single biggest destroyer of drains. They do not smash their way in; they find a weeping joint or hairline crack, follow the moisture, and grow. Once inside, a root thickens, forces the crack wider and builds a net that catches everything flowing past. Willows, poplars, oaks and even mature hedges are all capable of it, and the tree does not need to be directly above the pipe.
Ground movement
Soil expands, shrinks and settles with the seasons, particularly through wet winters and dry summers. Pipes laid decades ago move with it. Joints pull apart, sections drop out of line, and rigid old pipes crack where flexible modern ones would flex.
Age and material
A huge number of homes in this patch still run on original clay drains, and many mid-century properties have pitch fibre pipes that deform and blister with age. Clay is durable but brittle, and a century of use, root pressure and ground movement takes its toll. Old joints sealed with mortar rather than rubber are a weak point on every run.
Loads from above
Drains under driveways, extensions and parking areas carry weight they were never designed for. A shallow run under a spot where vans or delivery lorries now turn is a common failure point, and building work involving heavy plant can crack a pipe in a single afternoon.
Poor installation or previous bodges
Badly bedded pipes, wrong falls, and past "repairs" done with whatever was to hand all shorten a drain's life. We regularly find a modern plastic section joined to old clay with nothing but hope holding the joint together.
The warning signs of a broken drain
You cannot see a buried pipe, but a cracked drain leaves clues above ground. One sign alone proves little; two or three together justify getting the camera in.
| Sign | What it suggests |
|---|---|
| Drains keep blocking in the same place | Roots, a dropped joint or a deformed section snagging waste on every pass |
| Persistent foul smell outside or inside | Waste water escaping into the ground, or air pulled through a defect |
| Damp patch on a wall or floor with no plumbing explanation | A leaking drain wetting the ground beside the foundations |
| A strip of lawn greener and lusher than the rest | The garden is being quietly fertilised by a leaking foul drain |
| Sunken, cracked or lifting paving along the drain line | Washed-out ground beneath, where soil is being drawn into the broken pipe |
| Rats in the garden or under the house | Rats travel drain runs and exploit any breach to get out into the ground |
| Gurgling and slow drainage across several fittings | A partial collapse restricting the whole run rather than one blockage |
The subsidence question deserves a straight answer. A leaking drain that washes soil away from beneath foundations can contribute to ground movement over time. That is a slow process and not the usual outcome, but it is exactly why a suspected broken drain near the house is worth confirming sooner rather than later.
How a cracked drain is confirmed
Guesswork is expensive with buried pipes, so the professional approach is to look inside. A CCTV drain survey puts a camera through the run and shows exactly what is going on: the location of any crack or fracture, roots at a joint, displaced or dropped sections, and how bad the damage actually is. Crucially, the survey records the position and depth of each defect, which means any repair can be targeted at the damaged metre or two of pipe rather than the whole run. If you are weighing up what a survey involves and costs, our CCTV drain survey cost guide covers it honestly.
Repair options: patch, lining or excavation
The right fix depends entirely on what the camera finds, which is one more reason to survey before anyone quotes for repairs.
Localised patch repair
A single crack, open joint or root entry point can often be sealed with a patch: a resin-impregnated sleeve positioned over the defect and cured in place. No digging, minimal disruption, and the rest of the sound pipe is left alone.
Drain lining
Where a longer stretch is cracked or root-damaged but still holds its shape, a full liner creates a new structural pipe inside the old one. It seals every crack and joint along the length in one operation, and a properly installed liner is generally expected to last for decades. Our drain lining cost guide explains how the pricing works and when lining is the sensible choice.
Excavation and replacement
When a pipe has collapsed, deformed badly or lost its fall, lining has nothing sound to line and the damaged section has to be dug out and replaced. It is the most disruptive option, but a targeted dig guided by the survey footage is a far smaller job than the garden-wide excavation people fear. If you suspect things have gone beyond a crack, the signs and figures in our collapsed drain repair cost guide will help you gauge it.
All three routes are forms of professional drain repair, and an honest firm will recommend the least invasive one that genuinely fixes the problem, not the biggest job they can quote for.
Costs, insurance and responsibility
Repair costs vary widely with the length, depth and access of the damaged section, from a modest sum for a single patch up to a significant job for deep excavation, so treat any price given without camera footage with suspicion. Two checks before you spend anything. First, responsibility: you are generally responsible only for drains serving your property within your boundary; shared runs and pipes beyond the boundary usually belong to South West Water in this area, and if the defect is in their pipework the repair is theirs. Second, insurance: many buildings policies cover sudden accidental damage to underground services, though wear and tear and sometimes root damage are excluded. Insurers almost always want CCTV evidence, and our guide to blocked drains and home insurance covers how those claims tend to go.
Frequently asked questions
How do I know if my drain pipe is cracked?
The common warning signs are drains that keep blocking in the same place, persistent bad smells, unexplained damp patches, unusually lush strips of grass, sunken or cracked paving above the drain run, and rat activity. None of these proves a crack on its own; a CCTV drain survey is the only way to confirm one.
What causes drain pipes to crack?
The usual causes are tree and shrub roots forcing their way into joints, ground movement, age and corrosion in older clay or pitch fibre pipes, vehicles or heavy loads passing over shallow runs, and poor original installation. Many cracked drains have more than one cause working together.
Can a cracked drain pipe be repaired without digging?
Often, yes. Drain lining inserts a resin sleeve that cures inside the existing pipe, sealing cracks and open joints without excavation. Localised patch repairs work the same way over a single defect. Excavation is normally only needed when a pipe has collapsed or lost its shape entirely.
Is a cracked drain covered by home insurance?
Sometimes. Many buildings policies cover accidental damage to underground pipes, but most exclude wear and tear, and root damage is treated differently between insurers. A CCTV survey report showing the exact defect is usually the evidence an insurer asks for, so get the survey before assuming either way.
Who is responsible for a cracked drain pipe?
If the cracked section serves only your property and sits within your boundary, it is yours. Shared drains and pipes beyond your boundary are usually lateral drains or public sewers, which are the water company's responsibility, South West Water in this area. Confirm where the defect sits before paying for anything.
Think you have a cracked drain? Find out for certain
We survey, patch, line and repair damaged drains across Plymouth, south east Cornwall and south and west Devon. Camera first, honest recommendation second, fixed price before any work starts.
Call DCI Drainage on 07418 000 420 Fast, free quotes · Local, independent, not a franchise
