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What is Polybutylene Piping? (2021 Guide With Pictures)

Are you interested in learning about polybutylene water piping?

Poly was installed in millions of homes in the 80's and 90's, but we now know that it is a defective water pipe.

In this poly guide, I will go over...

  • The origin and history of polybutylene
  • How to identify poly (don't confuse with PEX)
  • The three main types of poly pipe systems
  • The big problem with polybutylene main water lines

Let's get started with this guide!

What Is Polybutylene?

Polybutylene is a type of plastic pipe that was manufactured for water supply in residential homes from 1978 to 1995. Unfortunately, this plastic piping is notorious for micro fracturing, split pipes, and subsequent home damage (and settled class-action lawsuits).

It is estimated that about 7 to 10 million homes in the U.S. had poly installed during this near 20 year period.  

The last year that you will likely find a home with poly is in 1996 due to built up supplies.  

Poly was also used for main water lines — from the home to the street — in single family homes.

Read Also: Tips & Traps When Buying A Home

Sometimes when we do a DIY job, such as replacing polybutylene, we spend a lot of time and money — and then end up hiring a pro to fix our mistakes. That's why I created my Contractor Search Tool, so my readers can get free quotes from local plumbers who are licensed and pre-vetted.

I invite you to at least see the pricing available from a few trusted plumbers—there is no obligation—and then you can decide whether to go ahead with a DIY job. Get your free quotes with my contractor search tool right here.

How Do I Identify Poly Piping?

Polybutylene usually has a grayish-blue appearance, but it can also come in silver, cream, or black — one region of the country typically has the same color.

In my neck of the woods (the D.C. area), poly usually has the typical bluish-gray appearance. One surefire way of identifying polybutylene is to look for the PB2110 mark stamped somewhere on the pipe.

Besides copper piping (which should be easily identifiable), you don’t want to confuse poly with other plastic piping such as PEX, CPVC, or PVC which are very common plastic water pipes.

PVC (a common white pipe) is only used for drain, waste, and vent piping and is not used for potable water.

PEX piping is usually red (for hot water) and blue (for cold water), but it can also be different colors and even clear-colored. PEX is also stamped with “PEX” somewhere along the pipe.

CPVC is a cream colored pipe with a yellow stripe along it’s length which is very common in newer homes due to the high cost of copper.

If you want to connect polybutylene to a new plumbing, I really like the SharkBite Brass Coupling. 

With this SharkBite polybutylene coupling, you don't need any special crimping tool, glue or even solder — and it is designed to connect poly to either copper, PVC, or CPVC. You can view the price of the SharkBite poly adapter here on Amazon.

Why Was Poly Installed In Homes?

Poly was originally made under the brand name Qest, and it was marketed to builders as a much cheaper alternative to copper piping. As far as builders knew, poly was a great material, approved by building codes, and it had excellent resistanceto freezing temperatures.

Easy Installation

Not only was poly significantly cheaper than copper, it could also shave days or even weeks off from a whole house plumbing installation; a very big advantage for builders.

In fact, installing poly was so easy to install that some plumbers even trained non-plumber employees to install it in homes.

Plumbers could also stop carrying around acetyl or propane tanks to each job site that was needed for sweating copper. The installers basically just needed one crimping tool to get the job done that saved a tremendous amount of work.

Rather than being soldered together like in copper (or glued together as in CPVC), poly was fastened together by using compression bands called “crimping”. Modern PEX piping still uses this compression/crimping style of installation. Poly was also much lighter than copper, so it was easier to carry to the job site.

At the time, poly manufacturers told builders and plumbers that it had a lifetime expectancy of 50 years, which we later found out to be far from the truth. On average, it only took about 12 years for problems with leaking poly pipes to show up.

Read Also: My Top Tools For Home Inspecting

How & Where Did Poly Leak?

In the beginning of the poly revolution, the majority of leaks happened at the fittings.

It was theorized that these leaks were mainly due to improper installation, exposure to UV light, improper storage, bad water chemistry, and other issues. This lead to changes in the fittings to try to solve the problems being reported with poly.

Plastic To Metal Fittings

The biggest change in the installation of poly was by replacing the use of plastic (acetal) fittings to metal fittings. The metal fittings were in the form of copper (or brass) AND they changed the compression bands from aluminum to copper. These changes at first seemed to work, and the leaks decreased.

Polybutylene with metal fittings and rings are undoubtedly the “least worst” type of poly piping installation method. However, even these metal fittings began to fail. And leaks were also showing up elsewhere along the pipe — not just at the fittings.

Chlorine Deterioration

What we know now is that polybutylene deteriorates in the presence of chlorine and other disinfectants in the public water supply. When poly was introduced in the late 1980’s, we simply did not know how this piping would stand up to chlorinated water.

Currently, we have advanced testing standards for the structural strength of plastic piping such as PEX and CPVC in the presence of chlorinated water that polybutylene was not subjected to in the 1970’s.

Location of Leaks

Unfortunately, it is impossible to know exactly where poly leaks will occur because it is an largely invisible process. The small cracks and flaking occur on the INTERIOR of the water piping, and these cracks eventually work their way outwards….where the leaks finally appear.

These leaks can occur gradually and slowly, or they can happen suddenly with a burst pipe and significant home damage.

Read Also: The Best Water Pressure Booster Pumps

What Are The Signs of a Home With Poly?

As a home inspector who has seen numerous homes with poly piping, the most obvious sign (besides the actual pipe) that a property has poly is numerous ceiling water stains.

During inspections, I always check moisture stains with a moisture meter to see if it's active. 

My favorite moisture meter is the AccuMaster because it comes with a sensor pad to use on flat walls like drywall as well as two metal pins to insert into soft objects like carpet.  You can view the price of the Accumaster on Amazon here.

From first hand experience, the homes with the most water stains were almost always homes with defective polybutylene water pipes.

Even if an owner completely replaces the poly piping, it is very difficult to remove the signs of every water stain. The contractor would be extremely good to leave no evidence of patching or paint cover ups — it’s almost impossible.

When I inspect a home, I’m looking at the ceilings with a high powered flashlight, and I can detect even very minor imperfections.

Read Also: The Best Moisture Meters (Find Hidden Leaks)

How Do Plumbing Leaks Cause Damage?

Mold Growth

Leaking poly piping can cause sizable damage to a home. When water leaks onto framing and drywall, it can result in mold growth not only inside the walls --- but the spores can be sent into the HVAC duct system.

Once you have detected any ceiling or wall leaks with a moisture meter, it is important to immediately remove all visible mold and to replace the poly piping.

A home's furnace can act as a central location to send mold spores throughout the entire home.

Whenever there is a mold problem in a home, I usually recommend installing an HVAC ultraviolet light which is installed at the furnace or air handler. My favorite HVAC UV Light is made by OdorStop.

These ultraviolet lights are high quality and even come with air flow sensors that turn on the UV light automatically.  You can see the price of OdorStop UV lights on Amazon here.

Wood Damage

Besides mold growth, leaking water pipes can damage the home’s wood framing, appliances, flooring, and furniture. 

Just one hidden leak may cause structural weakening of the home’s framing. Wood damage may result in sagging joists (and flooring) or other structural issues.

And if you add the damage resulting from several small leaks together, that alone can equal the costs of replacing the entire home’s piping; anywhere from $10,000 to $20,000 or more (depending on the size of the home).

One sudden and large pipe burst in a home — let’s say while you are on vacation — can lead to tens of thousands of dollars in damage.

Basement Covered in Mold

I did one home inspection on a home in Bowie, Maryland that ruined an entire finished basement. There was a small leak at a pipe in the basement, and it steadily released water while the homeowner was on vacation in a different country.

Unfortunately, the owner made the problem much worse because he turned off the air conditioning system which actually has a dehumidifying effect.

Well, when he got home, the entire basement was covered in mold — the ceiling, the walls, and even the floor.

The entire basement would have to be demolished and re-done, likely at a cost of at least $40,000. And this was all from one small plumbing leak (and turning off the a/c during the peak of summer). If you would like to check your house for mold, I recommend the DIY Mold Test. This home mold testing kit includes lab fees as well as an expert consultation. You can check out the price on Amazon here.

How Did Poly Change Over Time?

There were three main developments with poly, and each was introduced because of problems with leaking.

  1. Plastic fittings with aluminum compression bands
  2. Copper (or brass) fittings with copper bands
  3. The manifold or “home run” system

Plastic Fittings & Aluminum Rings

In the early years of poly, the pipes were connected with numerous acetal (plastic) fittings that were usually the same color as the poly piping. The very first plastic fittings were compression-type fittings also known as “grip” fittings.

Later on, plastic fittings were crimped to the poly pipes using aluminum rings.

There were approximately 10-20 plastic fittings from one plumbing fixture to the main water line; many possible points of failure.

Unfortunately, leaks occurred with significant damage to homes across the U.S.

Metal Fittings With Copper Rings

The next development occured when installers scrapped the problematic plastic fittings in favor of copper/brass fittings with copper rings.

This greatly reduced the problem of leaks at the fittings — at least for a while.

Unfortunately, leaks kept occurring, and lawsuits were brewing. Poly has been found to leak and rupture at potentially any location in the pipe, a plumbing mine field.

A study at the University of Illinois has shown that microfractures can occur at any point of the water pipe, and it can break or rupture without warning.

Nevertheless, poly went one step further in technological development…

The Manifold Or “Home Run” Poly System

The manifold was also an “improvement” on the poly system. The manifold or home run system simply means that there is a central location or “manifold” where every plumbing fixture directly connects to it.

So each plumbing fixture is isolated and doesn’t share water piping with any other fixtures. Modern PEX piping still commonly uses the manifold type of system.

This means that there are fewer fittings needed for each plumbing fixture. Without the manifold system, there would be about 20 fittings just for one plumbing fixture.

By using the manifold, the number of fittings was reduced to around 4-5.

Manifold Reduced Leaks

With fewer fittings, it meant less opportunity for leaks. In addition, the manifold could be easily monitored for leaking — a central area where the fittings are located.

Besides reducing the areas of possible leaks, it also greatly reduced the amount of time to install poly because of the fewer fittings. With manifold systems, a more flexible version of poly pipe was installed, and it typically came in rolls of 20 to 100 feet long.

In fact, the system became so easy to install, that plumbers even trained amateurs to install the manifold poly system. However, this lead to something else very interesting.

Because the manifold system used flexible poly piping, this gave the piping a very cheap and flimsy look as it was strapped to the ceilings and walls.

Builders wanted to hide this cheap and undesirable look. And that’s when they started installing copper stub outs to hide poly.

Read Also: The Best Hot Water Recirculating Pumps (Instant Hot Water)

Copper Stub Outs (Hidden Poly)

The copper stub outs (end piece copper sections) connect the plumbing fixture and go just to inside the wall cavity where it is connected to the poly. So if you looked under a sink, all you would see is copper!

The actual poly pipe is hidden behind the wall. As a home inspector, since I can’t drill holes in walls, all I can say is that the home appears to have copper piping even if there is poly hidden inside.

Poly Feeder Lines To Sinks

If you have a house built in the 1978 to 1996 time period, and even if you don’t have poly in your domestic water pipes, I would still check under all of the sinks for the supply lines. I still commonly find poly supply lines to bathroom sinks.

These smaller diameter poly pipes are also susceptible to chlorinated water and can be ticking time bombs.

If you are home, and it springs a leak, it may not be such a big issue. But what if a homeowner is on vacation? Just one small rupture in a sink feeder line can cause an untold amount of damage.

Pro Tip: Don’t confuse poly with PEX which is also commonly used in feeder lines.

Poly Feeder Lines

The Main Water Line (A Commonly Overlooked Issue)

Most real estate agents are now familiar with the problems with polybutylene piping in the home’s domestic water system — but most are unaware that a poly main water line can also be an equally hazardous problem (if not more).

A poly main water line in my area always has an intense blue color, and is easily distinguishable from copper or HDPE. HDPE is high density polyethylene which is always a black color. 

Almost all new homes now use HDPE for the main water line.

The main water line is as susceptible to chlorine as the smaller diameter branch piping inside the home.

Potential Foundation Damage

The potential damage with a ruptured main water line is a little different than inside a home. Imagine you are on vacation, and your main water line breaks. A massive amount of water is going to be deposited near the house.

As you might assume, water and foundations don’t mix.

As a home inspector, we are always harping about fixing the grading around the foundation (the ground should slope away from the home), and fixing poorly draining downspouts.

If hundreds of gallons of water are saturating the ground by the house, this increase in pressure can literally cause the foundation of the home to buckle — a phenomenon known as hydrostatic pressure.

So instead of water damage to the floor and drywall, a bursted main water line can literally move the entire house!

The costs of fixing a foundation problem like this could be astronomical.

What Happened To The Class Action Lawsuits?

There were two main class-action lawsuits in the 1990’s, Spencer Versus DuPont and Cox Versus Shell.

Shell and DuPont were two of the largest manufacturers of polybutylene. They both settled with the courts and have agreed to fund a settlement that has totaled around one billion dollars.

Both of these settlement funds have been depleted, and homeowners are now on their own.

Sometimes when we do a DIY job, such as replacing polybutylene, we spend a lot of time and money — and then end up hiring a pro to fix our mistakes. That's why I created my Contractor Search Tool, so my readers can get free quotes from local plumbers who are licensed and pre-vetted.

I invite you to at least see the pricing available from a few trusted plumbers—there is no obligation—and then you can decide whether to go ahead with a DIY job. Get your free quotes with my contractor search tool right here.

What's The Bottom Line On Poly?

Polybutylene was touted as an incredible plumbing invention when it first came out, but we now know it has come up very short (and very wet).

Like many construction product defects, the “final word” on the quality of a product can take many years and lawsuits to bear fruit.

I hope this guide has given you some quality information on polybutylene and some of the most important things about it’s history and use.

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7 thoughts on “What is Polybutylene Piping? (2021 Guide With Pictures)”

  1. Hello Arie,

    Thank you for this informative article.

    My question is; if a house has a crawl space instead of a basement, is the potential damage mainly now in the walls, and the cost of replacing the plumbing any less expensive?
    I was just about to submit an offer on a house in NC, and saw the type of plumbing in the declaration.
    Thank you.

    • Hi Sharon,

      If it is just a one level home, then the potential damage is mainly the walls, though the sub-floor, and floor joists could also get damaged. But yeah, the house is in a better situation with a crawl space because you can monitor most of the piping much more easily, and it will also be easier to replace. I always recommend getting quotes on poly replacement even if you don’t want to do it right now. There are companies called repiping specialists that specialize in poly replacement, I recommend getting at least 3 quotes.

      Good luck!

  2. If a home built in 2000 has a blue colored poly main line…is that a code violation? If so, would that not have been caught by the county before issuing the Certificate of Occupancy at the time of build?

    • Hi Jennifer,

      I can’t confirm that it’s poly, you will really have to call in a licensed plumber to make that call. And building codes will have to be relevant to your particular state. But I do suspect that it is likely polybutylene and that yes, it is likely a code violation, and maybe a lawsuit, lol.


    • Hi Marcelo,

      Poly piping is only used for supply piping and not drain piping so I wouldn’t worry about it. But yes, I think it theoretically could be have an impact if the drain piping was poly and pouring bleach down the drain was a consistent thing.


  3. I have samples of Poly B tubing that came from my boiler system (!) that are 30 years old. The pipe has no fissues, fractures, or signs of decay. It had some scale inside due to the rust from the boiler, but it was easily cleaned with some X400. Do you know who makes the most money from PB Pipe lies? Plumbers and lawyers. Don’t believe the hype. 99% of this mess was using the wrong compression fittings. The rest is all about fear and money.


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Arie Van Tuijl

I am a licensed home inspector in two U.S. states and the founder of Home Inspector Secrets. After performing hundreds of inspections, and seeing thousands of house defects, I realized people would love to have an online resource dedicated to home maintenance. I write detailed home guides and product reviews sprinkled with inspection tips. You can read my bio here.

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Home Inspector Secrets is an online resource for owners, buyers, and sellers to understand all aspects of home maintenance. We have detailed home guides, product reviews, inspection advice, and much more.