How to Connect PEX Tubing to a Water Heater

What You'll Need
PEX pipe
Brass fittings
Copper Crimp Ring
Crimp ring tool
Tubing cutter
Metal connector (copper stub)
Copper pipe
Brass manifold
Soldering torch
Solder paste
Pipe sealant

Cross-linked polyethylene or PEX tubing is commonly used in radiant heating systems. While other types of tubing require elbows, connectors and other fittings in order to complete a plumbing project, PEX tubing allows easier plumbing installation. PEX tubing is very flexible and easy to manipulate. It can can be crimped and bent to provide easier installation. In connecting PEX tubing to a water heater, do not do so directly. It is recommended to install a metal connector to the water heater first before connecting the PEX tubing. Here’s how:

Step 1 – Shut Down the Water Supply

Shut down the water supply first before working with the connection.

Step 2 – Connect the Metal Connector to the Water Heater

Before connecting the PEX pipe to the water heater, find a suitable metal connector to install onto the water heater. A copper stub-out elbow and a copper pipe will do. Connect one end of the stub-out elbow to the water heater by soldering the fitting. Cut a piece of copper pipe enough to connect the stub-out elbow to the flooring. Use the tubing cutter for this job. Solder the connections by following the next step.

Step 3 – Solder the Copper Stub to the Water Heater

Clean the copper tubing and the water heater fitting and apply solder paste evenly on the surfaces of the joint. Ignite the soldering torch and heat the joint evenly while applying solder. When the melted solder covers the joint entirely, allow it to cool. The solder will harden as it cools and will seal the connection between the water heater and the copper stub. Connect the copper pipe to the other end of the copper stub and apply the same soldering procedure.

Step 4 – Prepare the PEX Tubing

To prepare the PEX tubing, use a tubing cutter to cut at least a half inch of PEX to make sure the opening on the tubing is cut square. Slide a copper crimp ring over the pipe. Insert the brass fitting into the PEX tubing up to the shoulder of the fitting. Push the fitting back up to an 1/8 inch and make sure the copper crimp ring rests just over the brass fitting. Take the crimp ring tool, open the jaws and work it on the crimp ring to secure the fitting to the PEX tubing.

Step 5 – Connect the Manifold to the Copper Pipe

A brass manifold is an optional installation. However, it is important for several PEX tubing connections. Connect the brass manifold to the copper pipe and secure it using a pipe sealant. For a single PEX tubing connection, skip this step.

Step 6 – Connect the PEX Tubing

Connect the brass fitting on the PEX tubing directly to the copper pipe or to the brass manifold. Use a pipe sealant to secure the connection.