Polybutylene pipes: how to tell if you have them and what to do

Polybutylene is a flexible plastic water pipe, usually gray and sometimes blue or black, that went into a lot of homes built from about 1978 to 1995. It’s known for failing, especially at the fittings. To check, look for the stamp “PB2110” on exposed pipe near the water heater, under sinks, and where the main line comes in. If you find it, plan on replacing it, usually with PEX, but you don’t need to panic tonight.

How to tell if you have polybutylene

Grab a flashlight and look anywhere the water lines are exposed:

• At the water heater, where the hot and cold lines connect on top
• Under the kitchen and bathroom sinks, and behind the toilets
• Where the main water line comes into the house, often in the garage, a utility closet, or the crawlspace
• Running along the floor joists in the crawlspace, if you have one

The stamp is the tell. Polybutylene is usually printed with “PB2110” along its length. You might have to rotate your light around the pipe or wipe off some dust to find it.

A couple of things trip people up. The short pipe stubs coming out of the wall under a sink can be copper even when the pipe inside the wall is polybutylene. Looking under one sink and seeing copper doesn’t clear the house. Check the water heater and the crawlspace, where you can see longer runs.

Also, gray plastic isn’t automatically polybutylene. PEX, the pipe a lot of plumbers use today, comes in gray too, along with red, blue, and white. PEX is usually printed with “PEX,” so read the pipe before you worry.

Blue polybutylene was also used for the underground line from the meter to the house. If you can see where that line comes up out of the ground, check it too.

Why does polybutylene fail?

The general thinking is that the disinfectants in treated city water break down the plastic over time. The pipe gets brittle and can crack from the inside out, where you can’t see it. It may drip for a while, or it may let go all at once.

The fittings are the other weak spot. Early systems often used plastic fittings, and those are known for cracking. Later installs switched to metal fittings with copper crimp rings. Those hold up better, but a badly crimped ring can still leak. And the pipe between the fittings is the same age either way.

If you can see the fittings, note which kind you have. A plumber will want to know.

Is it likely in a North Alabama house?

Madison and a lot of the area around Huntsville saw heavy home building in the 1980s and 90s, right in the middle of polybutylene’s run. That doesn’t mean every house from that era has it. Plenty were built with copper, and plenty have been repiped since. But if your house went up in those years and nobody’s ever checked, it’s worth ten minutes with a flashlight.

What about insurance and selling the house?

Some insurers ask about polybutylene, and it can affect your coverage or your rate. If you have it, check with your insurer so you know where you stand before something leaks.

If you’re selling, expect a home inspector to flag it. Buyers often ask for it to be replaced or for a credit. If you’re buying, see our list of plumbing to check before you buy a house.

What to do if you have it

Replace it. Patching one leaking fitting fixes that fitting, but the rest of the pipe is just as old.

Most polybutylene repipes are done with PEX. It’s flexible, so it can be fished through walls and run through the attic or crawlspace with a lot fewer openings than people expect. You’ll usually have a few small drywall holes near fixtures to patch afterward, which beats tearing out whole walls.

How big a job it is depends on the size of the house, how many bathrooms you have, and whether there’s a crawlspace or an attic to work from. Call us and we’ll look at the house and give you a price before we start.

Find your main shutoff now. If you have polybutylene, know exactly where the main water shutoff is and make sure it turns. Here’s how to shut off the water to your house. If a fitting lets go, that’s the first thing you’ll need.

Just don’t leave it on the someday list for another ten years.