Pitch fibre was a popular drain pipe material in the UK, mainly from the 1950s to the 1970s. It was light, cheap and quick to lay, so it was widely used on housing estates built in that period. Many of these pipes are now reaching the end of their life.
What pitch fibre is
Pitch fibre pipes are made from wood or cellulose fibres impregnated with coal tar pitch. They are usually black and slightly soft compared with clay or plastic pipe.
Why pitch fibre fails
- Blistering: the inside of the pipe can blister and flake, especially where hot water and detergents from washing machines and dishwashers run through it.
- Deformation: the pipe can lose its round shape and flatten under the weight of the soil above, reducing the space for flow.
- Delamination: layers of the pipe wall can separate.
- Joint problems: joints can move, letting roots in.
Signs of a failing pitch fibre drain
- Blockages that keep returning in a drain from a house built between the 1950s and 1970s
- Slow drainage from several fittings
- Flakes of black material found when a drain is cleared
- Smells or damp near the drain run
See also signs of a broken drain pipe.
How to find out
A CCTV drain survey shows the pipe material and its condition: blistering, flattening, delamination or root ingress. It also shows how much of the run is affected, which matters for choosing the repair.
Repair options
The right option depends on how badly the pipe has deformed and where it runs:
- Minor blistering may be cleaned back carefully, though pitch fibre needs a gentle approach, as aggressive cleaning can damage it further.
- Lining from inside the pipe can be an option where the pipe still holds enough of its shape. Badly deformed pipe may first need re-rounding.
- Excavation and replacement with modern plastic pipe may be needed where the pipe has flattened badly or collapsed.
We explain the options available for your drain after a survey, and why we recommend one. See drain repairs.
Buying a house with pitch fibre drains
If you are buying a home built between the 1950s and 1970s, a drain survey before you exchange can tell you whether the drains are pitch fibre and what condition they are in. See drain surveys before buying a house.