Tree roots in the sewer: why that blockage keeps coming back

The pattern is recognisable: a blockage that clears nicely after jetting — and returns a few months later in exactly the same spot. Often the drains gurgle for a while first, the water runs away ever more slowly, and there is a tree, hedge or sizeable shrub near the sewer run. It is a classic especially with older house sewers of vitrified clay, with a joint every metre.

The explanation sits underground. Roots seek moisture, and a sewer pipe is the most reliable moisture source in the garden. Through the smallest gap or a shifted joint a rootlet grows inside, where it develops into a wig of fine roots in the damp pipe. That wig catches paper, grease and debris — and that is the clog you keep having removed. Jetting removes the clog, but not the root: it simply grows back, which is why the blockage usually returns faster each time.

There is little you can fix yourself here, but you can observe well. Track where and how often it goes wrong: the same drains, the same intervals? Note which trees or hedges stand above or next to the likely pipe run — the spot where the house connection leaves the plot is often on the building drawings. And use no chemical products: they never reach the root mass deeper in the pipe and only make the technician's work more dangerous. If you are planting new greenery, deliberately keep distance between deep-rooting trees and the pipe run: the cheapest prevention is the root that never gets close.

The real diagnosis comes from a camera inspection (€ 85-175): it shows exactly where the roots enter, how far the ingrowth reaches and whether the pipe is otherwise still sound. After that there are roughly three routes: removing the roots mechanically and jetting the pipe, repairing the leaking joint or damaged section, or — with a pipe that is failing in several places — replacing that section. If the ingrowth lies beyond the property boundary, the problem sits in the municipal sewer and the municipality is up.

Until the structural fix is in place, periodic preventive jetting (€ 95-175 per service) keeps the pipe workable — cheaper than an emergency job of € 125-350 every time the sewer picks its own moment. The full rates are in the price index.