Tree roots in drain pipes: signs and solutions

Roots grow towards moisture. Older clay drains were laid in short lengths with mortar or rigid joints, and over time those joints crack or open slightly. A small leak of water and warm air from the pipe draws fine roots straight to it. They slip through the gap, find a steady supply of water and nutrients inside, and grow.

Inside the pipe, those fine roots thicken and spread into a mat that catches paper, wipes and grease. Over years they can widen the gap, crack the pipe further or push sections out of line.

The symptoms build slowly. Drains empty more slowly than they used to. Blockages start happening, then keep happening, often in the same place. You may hear gurgling as water struggles past the obstruction. If there is a large tree or hedge near the line of the drain, roots are a strong possibility.

Roots can be removed. Jetting flushes out fine growth, and a mechanical cutting head deals with thicker masses. That restores flow, sometimes for quite a while. But the joint the roots came through is still open, and the tree is still there. The roots will come back.

A lasting fix seals the entry point. Where one or two joints are affected, a no-dig patch repair closes each one from inside. Where roots have entered along much of the run, drain relining seals every joint at once with a continuous new pipe.

Roots that have been in a pipe for many years can break it apart or push it so far out of line that there is nothing left to seal. In that case the affected section has to be dug out and replaced with modern pipe, which has flexible sealed joints that roots find much harder to get into. A survey after the roots are cut will show which situation you are in; our guide to drain repair costs explains how each route is priced.

If you are planting, it is wise to keep trees and large shrubs well away from the line of the drain; species with vigorous roots are best planted further away still. If a tree is already close to a drain, a sealed pipe is the best protection.

Where the tree belongs to a neighbour, or the pipe is shared, questions about who pays can come up. That is beyond the scope of this guide and depends on the circumstances; our guide on who is responsible for drains covers the basics of pipe ownership. Never cut or damage a protected tree without checking with your local council first.

Pruning a tree or hedge does not stop its roots seeking water underground, and removing a large tree can cause its own problems with ground movement. In most cases, the practical answer is to accept the tree and make sure the drain beside it is properly sealed. If you are unsure where your drain runs relative to a tree, a camera with a locating sonde can trace the line from the surface.

Avoid root-killing chemicals poured into the drain unless a professional has advised it; they can harm the tree and anything downstream without sealing the joint. Do not keep rodding a root blockage yourself, as rods can snag in the mass or damage an already weak pipe.

If you suspect roots, contact us and mention any trees or hedges near the drain. We can clear the pipe, show you the joints involved on camera and explain how to seal them.