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What Are Polybutylene Pipes

When investigating plumbing options, you may come across the term “polybutylene.” You may also find that this type of pipe was very popular until its mass failure in the 90s. How could a pipe that was supposed to be a product of the future fail so badly?

Polybutylene pipes certainly have many characteristics suited for durability and ease of installation. But they have one major flaw that caused a lot of trouble for homeowners and manufacturers.


Polybutylene is a type of moldable, inexpensive, and flexible plastic. For these reasons and its resistance to extreme temperatures and hydrostatic pressure, it was thought to be great residential piping material. But polybutylene reacts with chemicals in domestic water supplies and breaks.

Polybutylene Pipes are Plastic Water Pipes

Polybutylene pipes are simply pipes that are made out of a specific type of plastic known as polybutylene.

Man cutting the plastic pipe

This type of piping was very popular from about 1975 to 1995. It wasn’t installed in commercial buildings but in many residential ones.

It is estimated that six to ten million homes in America had polybutylene pipes installed. This comes out to one in every four or five new homes having polybutylene piping during this twenty-year period. 

Polybutylene pipes were meant to replace traditional copper piping and were used outside for underground water mains as well as inside to distribute interior water.

Unfortunately, these pipes were not as miraculous as they seemed, but that’ll be covered later.

Characteristics Suited to Piping

Easy to Mold and Shape

Polybutylene’s chemical structure allows for it to be easily molded and shaped without compromising its integrity. As plumbing pipes need to be bent into hollow and uniform tubes, this was advantageous to the production of polybutylene pipes.

Good Resistance to Hydrostatic Pressure

Hydrostatic pressure is the pressure that fluids (liquids and gases) exert on their surroundings as a result of gravity. As the name suggests, hydrostatic pressure is static, so it is the pressure exerted when the water is not in motion. 

For this reason, hydrostatic pressure can be thought of as the pressure inside the fluid, rather than the pressure exerted by it. 

Plumbing pipes carry water, although this water is not always in motion, making hydrostatic pressure a guaranteed occurrence in pipes. 

Polybutylene has a good resistance to hydrostatic pressure because of its durable design and resistance to thermal expansion. 

Thermal expansion is a large problem in most areas of plumbing. It’s one of the reasons why water heaters have relief valves and expansion tanks to combat thermal expansion

Illustration of thermal expansion in Polybutylene pipes

Being exposed to heat can warp pipes and compromise their integrity, but because polybutylene pipes are durable and experience only low amounts of thermal expansion, the effects of hydrostatic pressure are not felt as much by these pipes. 

Flexible

Not only are polybutylene pipes easy to shape and mold during production, but they are also flexible to facilitate ease of installation.

Relatively Inexpensive

Piping is extensive throughout the entire home, so the costs of piping can add up. For this reason, inexpensive piping is ideal.

Polybutylene pipes were relatively inexpensive because plastic can be manufactured much more cheaply than copper (the most popular alternative piping material), which must be mined and transported. 

While plastic piping for an entire home may cost from $4,200 to $6,000 on average, copper piping can cost from $5,000 to $20,000. As you can see, polybutylene pipes are a much more affordable option. 

Withstands Hot Water Well

Water supply pipes must withstand a range of temperatures. Hot water will often be encountered in a piping system.

It is natural for materials to grow in size when exposed to higher temperatures, but growing and then shrinking with changes in temperatures can fundamentally damage the structure of the material, making it more likely for the material to break. 

Although plastic has a higher susceptibility to thermal expansion than metal (they will expand and contract more readily in response to temperatures), polybutylene pipes are robust enough to withstand thermal expansion (the effects of the expansion and contraction aren’t as severe). 

Resists Freezing

Although hot water can cause trouble in pipes, preventing pipes from freezing is also a common concern. 

Polybutylene, as a material, resists freezing on a chemical level. The cold temperatures cause the plastic to shrink, but because it is so flexible it accommodates this shrinkage without resulting in breakages.

How Polybutylene pipe reacts to freezing level

In addition, when water freezes, it expands. So the flexibility in the outward direction also prevents the pipes from rupturing.

Polybutylene Pipes Have Been Banned

Although it may seem that polybutylene pipes are a great option for modern homes, this is unfortunately not the case. 

A few years after the boom in polybutylene pipe installation in 1975, major problems relating to the integrity of the pipes were discovered. 

The pipes were resistant to extreme temperatures and hydrostatic pressure, but something was causing cracks in the pipes and all the subsequent issues associated with this. 

It was discovered that cracks and leaking would occur within the first few years of installation, although it was more common after about 10-15 years.

Many lawsuits were filed against the pipe manufactures since the 1980s but two in 1995 finally shut down the use of polybutylene piping (at least in North American homes).

Major Failure of Polybutylene Pipes

The cracks in polybutylene pipes were not a product of extreme temperatures or hydrostatic pressure. Instead, they were from chemical reactions

This plastic seems to react with oxidants and disinfectants contained within the public water supply, such as chlorine. 

A chemical reaction between the plastic and these chemicals turns the wonder plastic into a brittle and flaky version of itself. This brittle and flaky material replacing the plastic causes microfractures to form in the pipes. 

Eventually, enough microfractures become large cracks and the pipes burst. 

So, it turned out that the polybutylene pipes were not a great replacement for the more expensive and rigid copper pipes after all. 

Subsequent Issues Caused

Bursting water pipes can have countless ripple effects that affect your home and your maintenance and repair outlay. 

With burst pipes, your plumbing system will not be operational. Wherever the water in the now-broken pipes was supposed to go, it will no longer reach this point. Because there are so many appliances in the home that need water, this can impact your daily life. 

The pipes must be repaired or replaced to make your plumbing operational again and to prevent further water damage. 

On the subject of water damage, there will be lots of it! Most pipes in the home hold a decent amount of water, so a burst pipe can easily damage an entire room or more.

Once insurance companies began to learn about the problem with polybutylene pipes, they had to adjust accordingly so that they wouldn’t have to pay for all of these expenses themselves. 

It is very likely that damage due to polybutylene pipes is not covered by your insurance. Not only will the pipes have to be replaced and water damage be repaired, but you are most likely going to have to pay for all of this yourself since your insurance is unlikely to help.

How To Identify Polybutylene Pipes

Rupturing polybutylene pipes in your home is a disastrous and expensive event. If you have polybutylene pipes in your home, it would be wise to replace them. That being said, how do you know if you have polybutylene pipes?

  • Polybutylene pipes are often gray or blue, but they can come in cream, black, or silver. 
  • They are often between a half-inch to an inch in diameter.
  • Color and size are not always reliable, so looking for the pipe’s stamp is the most reliable way to identify polybutylene pipes. The abbreviation for polybutylene is PB. A common serial number with this abbreviation is PB2110. If your pipes are stamped with this code, they are polybutylene pipes. 
  • As far as where to look, look at your supply pipes. Polybutylene pipes were never used for waste, drain, or vent pipes. They are often attached to your water heater, sinks, or toilets. They may also be located at your main shutoff valve or they may be exposed along your basement’s ceiling. 
How to Identify Polybutylene Pipes

Must They Be Replaced?

Although you are not legally required to replace polybutylene pipes if you were to find them in your home, it would certainly be advantageous to do so. 

Repiping a home can be expensive, but the life of your plumbing can be extended by at least 50 years. This makes the costs worth it in the long run if you plan on staying where you are long-term. 

It is also wise to repipe if your insurance does not cover damage to and due to polybutylene pipes since this would make a pipe bursting much more expensive. 

You can always take a gamble that the pipes won’t burst if you are only staying in the home short-term, but you will have to disclose the polybutylene pipes to the prospective new owners, which may make them pass on your property or lowball you in their offer.

So, polybutylene pipes can lower the value of your home if you are trying to sell it. It can also make the home more difficult to sell. 

Sources

https://costaide.com/polybutylene-pipe-replacement-cost/

https://www.dictionary.com/browse/hydrostatic-pressure

https://www.pbpsa.com/pipe-performance

https://www.polypipe.com/housing/blog/why-polybutylene-should-be-material-choice

https://www.punctualplumberdallas.com/blog/what-are-polybutylene-pipes-and-are-they-a-problem/

https://www.polybutylene.com/myths.html#:~:text=In%20most%20cases%20it%20takes,the%20buyer%20or%20prospective%20buyer.

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