How Does Pitch Fibre Rerounding Restore Pipe Shape?

Clay Drainage Systems

Pitch fibre pipes were widely installed across the United Kingdom from the post war period through to the 1970s. At the time, they were seen as a modern and economical alternative to traditional clay drainage systems. Decades later, many property owners are discovering that these pipes present a very specific set of challenges. One of the most effective modern solutions to these problems is pitch fibre rerounding, a specialist technique designed to restore the pipe to its original shape without excavation.

This article explains how pitch fibre rerounding works, why pitch fibre pipes deform in the first place, and how rerounding can restore structural integrity and flow capacity when applied correctly by experienced specialists.

Understanding pitch fibre pipes

Pitch fibre pipes are manufactured from wood cellulose fibres bound together with coal tar pitch. When new, the material is lightweight, smooth internally, and relatively flexible. However, pitch fibre was never intended to last indefinitely. Over time, exposure to moisture, ground movement, and chemical waste causes the material to soften and lose rigidity.

Unlike clay or plastic pipes, pitch fibre does not crack cleanly. Instead, it gradually deforms. The internal bore can change from a circular shape into an oval or even a flattened profile. This deformation is the root cause of many pitch fibre drainage problems.

Book in Today

Why pitch fibre pipes lose their shape

The primary issue with pitch fibre pipes is that the binding pitch material slowly breaks down. As this happens, the pipe walls become softer and more vulnerable to external pressure from surrounding soil. Ground settlement, traffic vibration, and even the weight of the property above can all contribute to distortion.

In addition, pitch fibre pipes are particularly susceptible to blistering. This occurs when the inner surface of the pipe swells and lifts, creating raised areas that restrict flow and catch debris. Over time, these blisters worsen, increasing the likelihood of blockages and slow drainage.

As deformation progresses, the effective diameter of the pipe reduces. Wastewater no longer flows freely, and repeated blockages become common. Left untreated, severe deformation can ultimately lead to collapse.

Request a Quote

What is pitch fibre rerounding?

Pitch fibre rerounding is a specialist mechanical process designed to restore a deformed pitch fibre pipe back to a near circular profile. Rather than removing and replacing the pipe, rerounding reshapes it from within.

The process uses a calibrated hydraulic or mechanical forming tool that is carefully drawn through the pipe. As it passes through, the tool applies controlled outward pressure, gradually reforming the pipe walls into their original shape.

This technique requires a deep understanding of pitch fibre material behaviour. Applied too aggressively, the pipe can fracture or delaminate. Applied correctly, rerounding can significantly improve both the shape and performance of the drainage system.

How rerounding restores pipe shape

The success of pitch fibre rerounding lies in controlled deformation rather than forceful expansion. The specialist equipment used is designed to expand incrementally, allowing the softened pipe material to be guided back into a circular form without tearing.

As the rerounding tool moves through the pipe, it compresses raised blisters and pushes flattened sections outward. This restores uniformity to the internal bore and removes the irregular surfaces that cause debris to accumulate.

Crucially, rerounding does not rely on heat or chemical treatment. It uses mechanical pressure alone, making it suitable for pipes that remain structurally intact but misshapen.

Once rerounding is complete, the pipe regains much of its original flow capacity. Water moves smoothly through the system, reducing the risk of future blockages.

The role of CCTV inspection

Before rerounding is attempted, a detailed CCTV drain survey is essential. Not all pitch fibre pipes are suitable candidates. Pipes that have fully collapsed, split longitudinally, or suffered advanced material breakdown may require replacement instead.

A CCTV inspection allows specialists to assess the degree of deformation, identify blistering, and confirm whether the pipe walls retain sufficient integrity. It also ensures that rerounding is carried out only where it will be safe and effective.

In many cases, rerounding is combined with drain lining to reinforce the restored pipe and extend its service life.

Rerounding versus full replacement

Traditional pitch fibre replacement involves excavation, often requiring disruption to gardens, driveways, or internal floors. It is time consuming, expensive, and disruptive.

Rerounding offers a no dig alternative where conditions allow. Because the pipe is accessed via existing inspection points, there is minimal disturbance to the property. Costs are typically lower, and work can often be completed within a single day.

While replacement remains necessary in some situations, rerounding provides a highly effective solution for many properties where the pipe has deformed but not failed structurally.

Rerounding versus full replacement

Traditional pitch fibre replacement involves excavation, often requiring disruption to gardens, driveways, or internal floors. It is time consuming, expensive, and disruptive.

While replacement remains necessary in some situations, rerounding provides a highly effective solution for many properties where the pipe has deformed but not failed structurally.

Contact our Team

When rerounding is suitable

Pitch fibre rerounding is most effective when deformation is present but the pipe remains continuous. Common suitable scenarios include ovalisation, mild to moderate flattening, and internal blistering.

Rerounding is not appropriate where the pipe has collapsed entirely, where sections are missing, or where the material has degraded beyond recovery. This is why specialist assessment is critical.

An experienced pitch fibre specialist will always recommend the most appropriate solution rather than applying rerounding indiscriminately.

Find out More

A measured approach to long term drainage health

Pitch fibre rerounding is not a temporary patch. When applied correctly and to the right pipes, it is a carefully engineered solution that restores function while preserving the surrounding property. It represents the balance between modern technology and respect for the limitations of legacy materials.

If you suspect your property may have pitch fibre drains or are experiencing repeated drainage issues, seeking specialist advice early can prevent unnecessary disruption and expense. A professional assessment can determine whether rerounding is suitable and ensure the right course of action is taken for the long term health of your drainage system.

Get in Touch With our Team