If your house was built between 1950 and 1980, your drains could be made of a product called pitch fibre. Pitch Fibre drain pipes cause a lot of issues. If you suspect that you have pitch fibre drain pipes it's important to determine the condition of them and to see if this is the reason your drains continue to block.

What is Pitch Fibre Sewer line?

Developed during the 40's as a new lighter and stronger material than traditional clay pipes. Pitch Fibre drain pipes were simple to manufacture and easy to install. Pitch Fibre was seen as the way forward and these drain pipes were laid up until the late 1970s.

Pitch fibre drain pipes are made of wood cellulose/fibre impregnated with coal tar. Often these have also had varying amounts of asbestos added to the material, used to add extra strength to the pipes. While these pipes were initially considered to be the new method of drainage, they suffered from some significant drawbacks.

Pitch fibre Pipe (left) vs Modern PVC Pipe (right)

The drawbacks of Pitch Fibre drain pipes

We have now learned that these drain pipes have a general working life of around 40 years meaning they are unlikely to outlast the clay pipes they were replacing. This means that even the last pipes laid in the 1970s are exceeding their projected lifetime. Furthermore, as lifestyles have changed throughout the years these drains have been subjected to greater volumes of cleaning chemical, oils and hot water than was anticipated previously. Chemicals and oils/fats are a bad idea for any drain but for pitch fibre drain pipes they can be incredibly problematic. Along with repeat quantities of hot water, these can soften the tar and cause delamination in the form of lumps/bubbles in the fibre. Weakening the material means that the pipes can deform underground and eventually, if left untreated, leak and collapse.

Solution

The first thing that needs to be done is a CCTV survey to establish if and where the pitch fibre extends to as it may not form the entirety of your sewers. Our CCTV survey will show any delamination (lumps, bumps and bubbles) in the line and identify the urgency of repair.

The repair work does require removal / decommissioning of the old sewer line to reinstate with new PVC as many of the "no-dig" or CIPP methods that use poly inserts will not be very satisfactory in such old pitch pipes.

This process does have other benefits however; the route of the old sewer line (sometimes under the house, garage or extension) can be changed / upgraded to comply with modern regulations and the correct inspection areas installed to replace old rodding eyes and interceptors.

If you would like more information or want to book one of our engineers to conduct a survey please don't hesitate to get in touch.