DRAINAGE REPAIRS AND NEW INSTALLATIONS

Pitch Fibre is a terrible product that is often found in schools, hospitals, housing estates and holiday parks built from the mid 1960s through to the early 1970`s.
It was introduced to the UK in the 1940`s as a lighter and cheaper option to vitrified clay.

Manufactured in lengths of 8ft with push fit joints (no sealing rings) it offered a quick and easy installation and was thought to be a modern flexible drainage system.
Thankfully the product was only used for a relatively short number of years due to the development of the modern underground plastic drainage systems, there are however many, many miles of pitch fibre pipe work systems coming to the end of their working life.
Pitch Fibre = Ticking Time Bomb
Unfortunately what we were actually installing was a pitch impregnated papier mache tube, which is now thought to have a design life of 40 years so stand by your beds the clock is ticking, and just when you thought there could not be a worse product beneath our schools, hospitals and housing estates there was at least one UK manufacturer who had the foresight to strengthen their pipe work using of all things asbestos fibre.

It will get you both ways, it collapses and becomes misshaped when under any kind of external pressure and as usual there was little specification for pipe bedding when it was installed so it relies on the sub-soil for external support.
The internal wall blisters and de-laminates when it comes into prolonged contact with water, which with hindsight is not the kind of product that we should have been giving a British Standard Mark to for the purpose of transferring waste and water from one point to another.
When surveyed, you often see sharp edges from bricks and masonry protruding through the pipe walls and the push fit collars within the system offer no resistance to tree root ingress.
The image above shows a cross section of a 100mm pitch fibre drain we excavated and you will note the large blister in the base of the pipe where the internal layers of the pipe wall have de-laminated, you can also clearly see how the pipe has lost its shape and therefore its structural integrity.

Repairing Pitch Fibre Pipe Work
We now have several repair methods available when pitch fibre systems fail. Which method should be used can only be determined after the system has been surveyed and assessed.
If the main defects are internal blistering and de-lamination with no major loss of shape, then the system can be re-rounded and relined using a Cipp lining method. However if there has been major deformation to the system then pipe bursting may prove to be a better option for renewal and of course there is always the traditional excavation method.
Each method has its own merits and more often than not excavation works will be required to some degree usually where junctions enter onto systems, as always a detailed CCTV Survey should be undertaken so that the best method or repair is utilised.