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Can I Use PEX Fittings On Polybutylene Pipe: Detailed Answer!

PEX fittings are common in plumbing work during PEX water piping installation or repair. However, when dealing with old polybutylene pipe installation and repairs, you require some modifications to ensure a proper connection.

But the question is, can I use PEX fittings on polybutylene pipes? Yes. You can use PEX fittings on polybutylene pipes but with connectors systems. Polybutylene (PB) pipes are larger than PEX fittings and thus require crimping connectors to ensure a secure connection.

This guide will discuss PEX fittings on polybutylene pipes and the necessary modifications required to ensure a secure connection. In addition, we shall cover the different types of PEX fittings and connector systems used on polybutylene pipes.

can i use pex fittings on polybutylene pipe

Can I Use PEX Pipe Fittings On Polybutylene Pipe?

Yes, with suitable connector systems, you can comfortably use PEX fittings on polybutylene pipes. PEX fittings are used to connect PEX pipes and, at times, these are used on copper pipes.

However, polybutylene pipes are not recommended for use with PEX fittings. That is because PB pipes are larger than PEX fittings and connectors. Their large size requires the use of crimping and compression fittings to bridge the gap between the two joints.

PB pipes have been in existence for long before the PEX pipes. They are preferred for their ability to bend around turns, eliminating the use of elbows for joints and turns.

Different Types Of PEX Fittings That Can Be Used On PB Pipes

There are different types of PEX fittings based on the method and materials used to make them. However, these types of fittings are all similar in quality as they have met the ASTM F876 and NSF/ANSI/CAN 61 standards for tubing.

Here are the three types of PEX fittings used in polybutylene pipes.

1. PEX Piping Crimp Fittings

Crimp piping fittings are the most common types readily available in the market at an affordable price. And there are two types of crimp fittings, namely,

  1. Brass PEX piping crimp fittings: These are made to the standard of ASTM F1807 from pure brass metal.
  2. Poly alloy PEX piping crimp fittings: Poly alloy consists of an alloy of brass and steel and conforms to ASTM F2159 standards.

Both fittings are connected to polybutylene pipes using the crimp or clamp method.

2. Push PEX Fittings

These push-to-connect fittings are most suitable for connecting polybutylene pipes as there is no need for complex tools or rings and clamps for a secure connection.

You only need a crimp connector to bridge the diameter difference and push the fitting to connect. The connection formed is secure and locks with a pop sound. And you require a disconnecting clip to remove the PEX fitting joint.

3. Expansion PEX Fittings

Though this type is rarely used due to its complex design, it can be used with polybutylene pipes with suitable connectors.

They are designed in two different types, namely,

  1. Uponor (Wirsbo) ProPEX expansion system
  2. Rehau RauPEX expansion system

4. Compression PEX-AL-PEX Fittings

Compression PEX-AL-PEX fittings have a split O-ring and a tightening nut to ensure a tight seal since it doesn’t use any connecting tools. These fittings apply the compression and lock mechanisms over the barbed edges.

5. Press PEX Fittings

Press PEX fittings are designed with preinstalled press sleeves, allowing for easier connection with polybutylene pipes. These fittings require pressing precision to avoid dislodging the connectors from their set position.

How To Connect A Polybutylene Pipe To PEX Fittings?

Connecting a polybutylene pipe (PB pipe) to PEX fittings requires the following tools and equipment to make secure connections.

  • The right type of connectors
  • Hacksaw/pipe cutter
  • Pinch or clamp tool

With the right tools, follow these procedures accordingly to make a PEX fitting and PB piping connection.

1. Choosing The Right Fitting Connector

Start by choosing the suitable connector to use on your PB pipe. Polybutylene pipes require gray collar transitional fittings.

2. Cutting The PB Pipe

You must do a clean cut on the PB pipe without scratching or making unnecessary dents. Care and precision are needed to reduce the damage on the cut edge.

When using a pipe cutter, follow the following steps.

Step 1: Mark the point at which you want to make the cutting

Step 2: Insert the pipe cutter and align it on the marked point

Step 3:  Rotate the pipe cutter as you tighten after every rotation until the pipe is cut

If you use a hacksaw or a reciprocating saw, follow the steps below.

Step 1: Mark the point at which you want to make the cutting

Step 2: Use a G-clamp to hold it firmly on a bench for support

Step 3: Position yourself at a perpendicular angle for a straight cut using the saw

3. Determining The Insertion Depth

After cutting the PB pipe, you need to determine the depth of insertion depending on the type of connector you will use.

Check on the recommended depth encrypted on the connector of your choice or check out the sharkbite pipe insertion depth chart. Mark the point on the pipe after determining the depth.

4. Insert The Connector

Insert and adjust the crimp connector to ensure proper insertion depth into the PB pipe. On the other end, fix the PEX fitting of your choice and complete the installation.

The connector acts as a compensation pipe to bridge the gap left by the diameter difference between the PB pipe and the PEX fitting.

5. Test The Connection By Running Water Through It

Run water in the pipe connection to check for any connectivity issues. Close the pipe end to check on the pressure effect. If there is no leakage, the connection is secure.


Below are the frequently asked questions. Keep reading to learn more!

Q: Can You Use PEX-Crimp Fittings On Polybutylene Pipes?

Yes. You can use crimp PEX fittings on PB pipes due to their reliability and ease of installation. However, using a crimp compression connector would be best to bridge the gaps between the pipes.

You can also use connecting tools such as a clamping lever to ensure a secure connection.

Q: Can I Glue A Polybutylene Pipe And PEX Fitting Connection?

No. Polybutylene pipes are designed for connection using fittings and connectors. Using glue and adhesives can cause leakages and loose joints that burst under pressure.

Use crimping connectors and a suitable fitting method for PB pipes to ensure a tight seal.

Q: Is It Possible To Determine The Size Of PEX Fittings To Use On Polybutylene Pipes?

Yes. It’s easy to determine the correct size of fittings for your PB pipes. Check the printings on the sides of the PEX fittings for the appropriate size ranging from 3/8” to 1”.

If the paintings have faded, use a vernier caliper to measure the outside diameter.


PEX fittings can be used on polybutylene pipes for installation and repair. However, due to their differing diameter sizes, it is safe to use a connector to bridge the gap and ensure a secure connection.

It would be best to use crimp connectors for polybutylene pipes due to their ease of installation and affordability. Since PB pipes are outdated, you can replace them with PEX or brass and copper pipes that are feasible with PEX fittings.