Insurers face a potential £100m repair bill for drainage problems caused by decaying pitch fibre water pipes, according to drainage specialists Dyno-Rod.

Pitch fibre pipes were widely used during the 1960s housing boom as a cheaper alternative to traditional ceramic pipes.

They were quickly outlawed by building inspectors, after it was discovered they had a limited life span and were expensive to repair. But pitch fibre pipes have been used in thousands of homes and are now reaching the end of their life span.

According to Margaret Burke, Royal & SunAlliance claims adviser for Cornwall: “Pitch fibre pipe drainage problems have been increasing steadily over the past few years and they are proving expensive to solve.”

Previously, replacing pitch fibre pipes would have meant extensive excavation and replacement work. The total bil is thought to be around £100m.

But Dyno-Rod is piloting a cheaper repair process in the south-west of England that involves relining damaged pipes with a fast-drying resin.

Burke said: “The new technique is offering us a huge saving, sometimes more than 50% compared to standard excavations.”

Dyno-Rod said it recently refurbished a domestic drainage system in just five hours compared to three days for a full excavation and saved £2,500.

Ken Scott, Dyno-Rod spokesman, said: “We completed a job at a commercial site for £50,000. With excavation the cost would have more than doubled.”

Insurance Ombudsman Michael Lovegrove admitted the industry faced a problem over pitch fibre pipes, but only in so far that insurers faced claims for accidental damage.

He said: “This is not a big issue and there has not been an upsurge in claims. We have received only a handful of complaints concerning pitch fibre pipes.”

Lovegrove said it was usual for household insurance policies to exclude damage from wear and tear or construction defects. He added that home owners without accidental damage cover would have to pick up the bill for repairing pitch fibre pipes, unless the damage was caused by an intervening peril such as a flood.