When tackling a residential plumbing project, the transition from rigid copper piping to flexible PEX tubing often presents a unique challenge. This specific connection point is known as a stub out, and mastering how to use pex copper stub out fittings is essential for a leak-proof and code-compliant installation. This process requires precision and the right components to ensure a durable and efficient water supply system.
Understanding the Stub Out Fitting
The term "stub out" refers to a short length of pipe that terminates at a wall or surface, creating a connection point for a future fixture. In the context of combining PEX and copper, the fitting is the critical component that bridges the two materials. You cannot directly crimp a PEX ring onto a copper pipe, so the fitting must accommodate both.
Typically, the copper stub out features a male thread on one end that screws into a female port on the valve or manifold. The opposite end is either soldered into the copper main line or connected via a push-fit connector. The other side of the stub out provides a barb or a crimping port specifically designed for securing the PEX tubing.
Material Compatibility and Code
Plumbing codes vary by jurisdiction, but most local inspectors require the use of dielectric unions when connecting dissimilar metals like copper and PEX. A dielectric union contains a plastic sleeve that separates the copper and brass components, preventing galvanic corrosion. While a standard soldered or compression stub out might function, using a dielectric union is the professional and legally safe approach to ensure longevity.
Tools and Materials Required
Before beginning the installation, gather all necessary tools to avoid mid-project delays. For a soldered connection, you will need a torch, flux, solder, and emery cloth. For a push-fit system, you will require a dedicated PEX cutter and crimping tool. Regardless of the method, a pipe cutter and a variety of wrenches are essential.
- Copper pipe cutter
- Adjustable wrenches or channel-lock pliers
- Torch kit and lead-free solder (for soldered method)
- PEX crimping tool and copper crimp rings
- Dielectric unions (recommended)
- PEX tubing cutter
Step-by-Step Soldered Method
The traditional soldered method provides a robust connection that has stood the test of time in plumbing. This technique involves preparing the copper surfaces, applying flux, and heating the joint to melt the solder.
- Cut the copper pipe to the desired length using a pipe cutter to ensure a clean, square edge.
- Deburr the inside and outside of the cut pipe with a deburring tool to remove sharp edges that could puncture the PEX.
- Thoroughly clean the pipe and fitting with emery cloth until the metal is bright and shiny.
- Apply a thin layer of plumbing flux to the cleaned pipe and fitting to prevent oxidation during heating.
- Heat the fitting evenly with a torch and introduce solder into the joint. The solder will be drawn into the gap by capillary action.
- Allow the joint to cool completely before handling or putting pressure on the line.
Using Push-Fit Connectors for Speed
For those looking to expedite the process without compromising quality, push-fit connectors offer a modern alternative to soldering. These fittings utilize a rubber gasket and a gripping mechanism to secure the PEX tubing, eliminating the need for open flames.
To use this method, you simply insert the prepared PEX end firmly into the PEX side of the push-fit stub out until you hear or feel it lock into place. It is crucial to ensure the tubing is cut perfectly square; any deviation can lead to leaks. Once installed, the tubing can be easily removed and reinserted if adjustments are necessary.
Finalizing the Connection
Once the stub out is physically connected to the copper line—whether through solder or a mechanical clamp—the final steps involve attaching the PEX tubing. If using a crimp ring system, slide a copper crimp ring over the PEX tubing and insert the tubing into the barb of the stub out. Use the crimping tool to compress the ring, creating a tight seal. Always verify the connection with a manual pull test to ensure it is secure before restoring water pressure.
