Polybutylene piping is a low-cost piping formed of plastic resin. It is commonly gray, white, or sometimes black in color. Polybutylene piping was used as a substitute for copper piping in both underground water mains and interior plumbing. Due to the ease of installing poly piping, it was used in the construction of about 20% of homes built throughout the U.S. between 1978 and 1995; however, it has been discovered that as poly pipe ages and reacts with water-soluble oxidants, it begins to degrade and can leak, causing severe damage to the surrounding building structure. It is believed that Polybutylene Pipe was installed in that period of time.

Problems With Polybutylene

Although some poly piping problems stem from improper installation, most complaints are with the integrity of the piping itself. Polybutylene pipe is known to deteriorate due to contact with oxidants normally found in public water supplies. The failure can occur in the plastic fittings or in the pipe itself. A main concern regarding poly pipe is that, since the oxidants are carried in the water, the pipe deteriorates from the inside. This makes it very difficult to determine if the pipe is truly in good condition. Most home inspectors cannot give a reliable assessment on the condition of poly piping unless there is a visible problem with the exterior of the pipe or its installation. In addition, when a leak occurs, it may be extremely severe because the deterioration occurs from within.

Poly pipe leaks are unpredictable and there are no symptoms to warn of an impending leak. Some factors that affect polybutylene piping adversely can include:

• Poor installation
• Water quality
• Pipe age
• Chlorine levels
• Deterioration of fittings (both metal and plastic)

When polybutylene pipe reacts with the oxidants in normal tapwater, it becomes brittle, sometimes scaling or flaking. This results in a fracturing of the interior surface of the pipe, which allows for more deterioration. Eventually the pipe will begin to leak, causing damage throughout a home. Poly pipe with plastic fittings or with metal fittings will eventually incur damage; poly piping is not a reliable piping under any circumstances. If a pipe has been leaking for some time without the knowledge of a homeowner, severe structural damage to the home can result, making repairs extremely difficult.

Damage from polybutylene pipe leaks can be expensive, in some cases more than the original cost of the house. Insurance companies sometimes cancel or refuse policies for homes with known poly piping problems, and it is difficult to market a home that has such an unreliable plumbing system.

How to Tell If You Have Poly

Exterior – Polybutylene underground water mains are usually blue, gray or black. It is usually 3/4″ or 1″ in diameter, and it may be found entering your home at the meter (if located inside) or where the main shutoff valve is located.

Interior – Interior polybutylene pipes are typically gray in color and are usually visible by your water heater and leading to sinks and toilets. In many cases, polybutylene and copper was used in combination, so even though you may see copper pipe coming out of the wall, polybutylene may still be in place behind your walls and ceilings.

Will the Pipes Fail?

It has been reported that the additives used in fighting bacteria, like chlorine, attack parts of polybutylene pipe and fittings leading to cracking and ultimate failure of the system. Unfortunately there’s a misconception that if your pipes haven’t leaked yet, they never will. This is not true. The longer polybutylene is in use, the greater the chance of having a major leak. Polybutylene pipe with plastic fittings or metal fittings will eventually fail. It is believed that other factors including improper installations can contribute to the failures of polybutylene piping.

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