What Polybutylene Actually Is
Polybutylene is a plastic resin used for water supply piping from approximately 1978 to 1995. It was cheap, flexible, and easy to install. Builders loved it. About 10 million homes were plumbed with the stuff.
The problem is chlorine. Municipal water treatment uses chlorine to kill bacteria, and chlorine degrades polybutylene from the inside. The pipe becomes brittle and eventually fails. Sometimes at a joint. Sometimes in the middle of a run. Sometimes in the wall where you can't see it until water starts coming through the ceiling.
There's no reliable way to predict when a particular section of pipe will fail. Some pipes lasted three years. Some have lasted thirty. The class action lawsuit in the 1990s resulted in a settlement fund, but that money ran out years ago.
Janet's Story: The Insurance Problem
Janet called me after an inspection I did for her back in 2019. She'd bought a ranch house in a subdivision built in 1987. Classic polybutylene neighborhood. Every house on the street had the same gray pipes.
"My insurance just non-renewed me," she said. "They say they won't cover water damage from polybutylene anymore."
She'd been in the house three years with no problems. Not a single leak. But her insurance company had changed their underwriting guidelines, and polybutylene was now on the exclusion list. She had 60 days to find new coverage or repipe the house.
The Numbers
Janet got three quotes for repiping. They ranged from $5,800 to $8,200. The differences came down to approach and materials. The low bid was for PEX with open wall access where possible. The high bid was all copper with drywall repair included.
She went with the middle quote: $6,400 for PEX throughout, patching walls herself afterward. The plumbers were done in two days. The drywall repair took her a month of weekends.
"I'm not even mad about the money," she told me. "I'm mad that nobody warned me this could happen. The inspection mentioned the pipes, but I didn't understand what that meant."
That conversation changed how I explain polybutylene to clients. I spell out the insurance implications in plain language now.
Marcus and the Midnight Flood
Marcus found out his polybutylene was failing at 2 AM on a Tuesday. He woke up to the sound of water running somewhere it shouldn't be.
The split was in a supply line inside the wall between his kitchen and dining room. By the time he found the main shut-off, he had an inch of standing water in both rooms. The hardwood floor was ruined. The bottom two feet of drywall was soaked. Insulation in the exterior wall had to be replaced.
His insurance covered most of it. About $22,000 in damage. But they wouldn't cover the repiping itself, which he had to do anyway once they cut open the walls.
What Failed
The plumber showed Marcus the pipe section that failed. It looked fine from the outside. But when he squeezed it, it crumbled like a stale cookie.
"This is what happens," the plumber said. "It gets brittle and then one day the pressure is just enough to crack it."
Marcus had owned the house for eight years. He knew about the polybutylene. He'd even priced repiping a few times. But nothing was leaking, and eight grand seemed like a lot to spend on pipes that were working fine.
"I could have done it for eight," he said. "Instead I'm doing it for eight plus twenty-two in water damage minus what insurance didn't cover. Plus a month in a hotel while the floors dried out."
He sends me pictures every year on the anniversary. The new PEX pipes are bright red and blue behind his wall. "Never again," the caption always says.
The Wait-and-See Approach
Not everyone with polybutylene ends up with a disaster story. My neighbors Tom and Rita bought their house in 1992. It came with the original polybutylene plumbing from when the house was built in 1986.
Thirty-eight years later, they're still using those same pipes.
No leaks. No failures. No problems at all. They've replaced three water heaters, two furnaces, and the entire roof, but the gray pipes keep working.
"We know it's a risk," Tom told me over the fence one afternoon. "But we're 72. We're not planning to be here another thirty years. If it fails, insurance covers it. If it doesn't, we saved seven thousand dollars."
Why Some Pipes Last
There's no definitive answer for why some polybutylene installations fail quickly and others last decades. Theories include:
- Variations in pipe manufacturing quality
- Different chlorine levels in local water supplies
- Installation technique affecting stress on joints
- Temperature fluctuations stressing the material
- Just plain luck
The honest truth is that nobody knows for certain. Some experts say all polybutylene will eventually fail. Others say the worst batches already failed years ago and what's left might be fine.
I can't tell Tom and Rita what to do. They're adults making an informed decision about their own risk tolerance. But I've also been to houses where the failure happened right after someone decided to wait and see.
What I Tell Buyers Now
When I find polybutylene in a house, I cover three things in detail.
First, the insurance situation. Some companies won't write new policies for homes with polybutylene. Others charge higher premiums. A few don't care. I tell buyers to get insurance quotes before finalizing their offer, not after. Finding out you can't get affordable coverage after you're under contract is a bad surprise.
Second, the replacement cost. I give a ballpark range based on the house size and what I can see of the plumbing layout. Two-bathroom ranch, maybe $5,000-7,000. Four-bathroom two-story with finished basement, probably $8,000-12,000. These aren't bids, just rough numbers for planning purposes.
Third, the risk. I can't predict when or if the pipes will fail. I can tell them that failure is well-documented, that it happens without warning, and that water damage from a burst pipe inside a wall is expensive and disruptive to repair.
The Negotiation Angle
Polybutylene gives buyers negotiating leverage. Sellers in neighborhoods with widespread polybutylene usually know it's an issue. They've watched neighbors repipe. They've probably dealt with insurance questions themselves.
Most transactions I see involve either a price reduction or a repair credit. The amount varies by market conditions. In a hot market, sellers might give back a few thousand. In a softer market, I've seen full repiping costs credited at closing.
The key is getting actual quotes, not just estimates from the internet. When you present a seller with three written bids from licensed plumbers, the conversation becomes about real numbers rather than speculation.
How to Identify Polybutylene
Polybutylene is usually gray, though some is white or black. It's flexible plastic, about the diameter of a pencil for half-inch lines and a marker for three-quarter-inch lines. Look for it:
- Under sinks at the shut-off valves
- Near the water heater
- At the main water shut-off
- In unfinished basements and crawl spaces
- In the water meter box (this is the supply side, may differ from interior)
The pipe is often stamped with "PB" followed by a number. Common markings include PB2110 and PB2120.
Don't confuse it with PEX, which is also flexible plastic. PEX is usually red, blue, or white. It's cross-linked polyethylene, a completely different material without the same failure history.
The Bottom Line
I've been in this business long enough to know that some polybutylene pipes will work for another twenty years without incident. I've also been in enough flooded basements to know what happens when they don't.
If I was buying a house with polybutylene, I would negotiate the replacement cost into the deal. I would get it repiped before I moved furniture in. And I would sleep better at night knowing that one particular surprise was off the table.
But that's me. Your risk tolerance, your budget, and your circumstances are yours to evaluate. I just want you to make that decision with your eyes open, not because you didn't know the pipes in your walls were time bombs.