Updated
Tree Roots In The Drain
The same run blocks again every few months, and what comes out is fibrous rather than what was flushed.
Find a drainage engineer
What's happening?
Roots do not break into sound pipes; they find pipes that are already imperfect. A hairline crack, an open joint on an old clay drain, or a poorly made connection leaks a little moisture into the surrounding soil, and roots grow towards it. Once a fine root reaches the crack it thickens inside the pipe, branches, and forms a mesh across the bore that catches everything passing — paper, wipes, fat — until the run blocks. The classic signature is repetition: cleared in the spring, blocked again by the autumn, and again the following year, always in the same place. Cutting the roots out restores flow but does not remove the reason they came, which is why a root problem is really a pipe repair problem.
What usually causes it?
- Open or perished joints on Victorian and mid-century clay drainage
- A hairline fracture from ground movement, heavy vehicles or nearby excavation
- A badly made connection where a later extension or bathroom was tied in
- Willow, poplar, birch and other water-seeking species planted close to the run
- A leaking joint at an inspection chamber's benching
- Shallow drainage under a garden or a driveway with no protective surround
- A previous root cut with no lining or repair, so regrowth was inevitable
Is it dangerous?
Not directly, but it is progressive. Roots widen the defect they entered through, and a crack that started as a hairline ends up as a displaced joint and then a collapse. The blockages themselves bring the usual sewage risks when they back up. Trees can also be protected — a preservation order or a conservation area means you cannot simply remove the tree — so the drainage answer usually has to be repairing the pipe rather than removing the roots' source.
Can I fix it myself?
Recognising the pattern is the useful contribution. If a run blocks repeatedly at the same point, keep a note of the dates and what came out; fibrous, hair-like material rather than paper and wipes strongly suggests roots. You can also map the trees within about ten metres of the run. Do not attempt root cutting yourself — the tools that do it are mechanical cutters run down the pipe, and using rods hard against a cracked clay drain is a good way to turn a crack into a collapse.
When should you call a drainage engineer?
Call a drainage engineer at the second repeat blockage rather than the fifth. Ask specifically for a CCTV survey with a report, because the survey is what turns a recurring cost into a one-off repair: it locates the ingress, measures the depth, and shows whether the pipe can be lined or has to be dug up. If the tree is protected or belongs to a neighbour or the council, the survey report is also what you will need to discuss it with them.
What will the drainage engineer actually do?
- Cut the root mass out mechanically and jet the run clear
- Run a CCTV survey to locate the ingress point, its depth and the condition of the pipe
- Produce a report with distances and defect grading suitable for insurers and for planning the repair
- Line the affected length with a cured-in-place liner, or patch-line a single joint, to seal the ingress
- Excavate and replace the section where the pipe is too damaged to line
- Re-survey after the repair to prove the run is sealed and free flowing
Frequently asked questions
We’re happy to answer all your questions.
Need a drainage engineer?
Compare local drainage engineers on Tradehand — coverage areas, accreditations and phone numbers, no middleman.