Pitch Fibre Drains: Problems, Surveys and Relining

What is pitch fibre pipe?

Pitch fibre pipe is made from wood or cellulose fibres bonded together and soaked in coal tar pitch, formed into a tube. It is black, fairly thin-walled and much lighter than clay. The same kind of pipe was used in the United States, where it is often called Orangeburg pipe after the town where it was made. In the UK it was mostly used for foul and surface water drains around houses, rather than for public sewers.

How pitch fibre drains fail

The weakness of pitch fibre is that it is relatively soft. Over time, the weight of the soil above and traffic on drives can squash the pipe out of round, a process called deformation or ovality. The inner layers can also blister and lift, especially where hot water and detergents from kitchens and washing machines have run through it for years. The blisters narrow the bore and catch waste.

• Pipe squashed into an oval or flattened shape
• Blistering or flaking of the inner wall
• Splits along the length of the pipe
• Joints that have pulled apart or let roots in
• Repeated blockages at the same point

Signs you might have a pitch fibre problem

There is often nothing to see above ground until the pipe has narrowed enough to block. Typical warnings are a drain that blocks repeatedly although nothing unusual is going down it, slow drainage from several fittings, or waste backing up into a gully. On some homes, a dip in the lawn or drive over the line of the drain suggests the pipe beneath has deformed or collapsed.

Homebuyer surveys on houses of this age often flag pitch fibre as something to check, because a deformed drain can be an expensive surprise after purchase.

Confirming it with a camera survey

The only reliable way to know what material your drains are and what state they are in is to look inside. A CCTV camera passed along the drain shows the pipe material, whether it is still round, where blisters or splits are, and how far along each defect sits. That record decides which repair is possible. It is also worth having before an extension is built over an old drain, or as part of buying a house from this period.

Repair options

Where a pitch fibre pipe has blistered or split but is still close to its original shape, relining is often possible. The pipe is cleaned carefully, then a resin-soaked liner is inserted and cured in place to form a new pipe inside the old one, without digging. Care is needed with cleaning: high pressure must be matched to the soft material so the pipe is not damaged further.

Mild deformation can sometimes be corrected by specialist re-rounding before lining. Where the pipe is badly flattened or has collapsed, there is not enough of it left to line, and that section needs excavating and replacing with modern pipe. Many repairs combine the two: lining the sound lengths and replacing the worst.

What affects the cost

The cost of dealing with a pitch fibre drain depends on how much of it is affected, the pipe diameter, how deep it is, what is built over it and whether lining or excavation is needed. A short deformed section near a chamber is a very different job from a long run under a monoblock drive. A survey with measured defect positions lets you compare options properly.

Questions we get asked