Polybutylene pipes used in plumbing may show no outward signs of distress even when they are close to bursting. Found in as many as one in five homes built between built between 1978 and 1995, polybutylene piping can leak at joints and unions behind walls where they can cause mold.

"Polybutylene pipe generally fails after 10-15 years of use," says Carl Brahe, registered home inspector. "It is unpredictable when it will fail, but it is certain that it will fail."

Normal home inspections may not uncover the piping, say experts, so where it is most likely to be found and what can be done about it?

Polybutylene pipe may be used anywhere in the plumbing system, inside or out, says Brahe, but the most likely places to find polybutylene pipe are:

Inside:

• Entering the water heater

• Crossing basement ceilings

• Feeding sinks, toilets, and bathtubs

Outside:

• Entering the home through basement walls, etc

• Attached to your home's main water shutoff valve

• Attached to your home's water meter

• Main water service from the meter entering the house

• Copper pipe may be attached to poly pipe somewhere underground. Copper may be at either end of the main water supply.

If your seller or buyer finds polybutylene pipe, recommend the following:

"The first thing to do if you discover polybutylene pipe in your house is to contact The Plumbing Claims Group at 800-356-3496," says Brahe. "This is the contact for the insurance settlement supplied by the manufacturers of polybutylene. There are limitations on payments. You must have experienced leaks and there are age limitations. If you qualify, the settlement seems generous, but limitations may exclude your home."

He says, "The only way to prevent damage that will come from this plumbing is to replace it. Specialists claim that they can replace a polybutylene system, in an average house, with copper for about the price of a re-carpet. They have developed methods to cause minimal damage during the remediation cutting costs and time requirements. Average remediation time is claimed to be one week."

Brahe suggests that re-piping may involve:

• Excavation with a trencher. A small trench is dug to replace pipe in areas where the freeze depth is shallow.

• Pipe-splitting. A wedge is pulled through the polybutylene pipe splitting as it moves through the old pipe. A new copper pipe is pulled behind the splitter. The new pipe is installed without digging.

• Deep trench excavation. In areas where pipes must be buried deeper, and feeding the new pipe behind a splitter doesn't work, a deep trench must be dug the length of the main water line.

• Cutting holes in walls and floors. The polybutylene replacement specialists have developed methods to minimize hole-cutting. If there has already been damage to your home from a poly pipe leak, then the cost of re-piping and repairing your home will be increased considerably.

Realtors should be concerned about houses with polybutylene plumbing. They're harder to sell and have the possibility of legal action from buyers against sellers, inspectors and brokers, warns Brahe.

"These houses need remediation and have an escalating probability of water damage occurring as replacement is delayed. If you are involved with a house built between 1978 and 1995 that has any kind of plastic water lines, assume it is polybutylene until you find out differently."