How to Replace Grey Polybutylene Pipe with PEX

Thoroughly inspect the entire house to locate all runs of grey polybutylene pipe. Identify the main water shutoff valve, the water heater, and every plumbing fixture (sinks, toilets, showers, outdoor spigots). Using a notepad, pen, and measuring tape, sketch a diagram of the current system. Plan the location for the new PEX manifold, typically in a utility room or basement near the water heater. Based on this plan, create a detailed materials list, calculating the required lengths of red PEX (for hot water) and blue PEX (for cold water), and counting every fitting, valve, and clamp you will need. A stud finder can help anticipate routing challenges through walls.

With your detailed list, purchase all the necessary tools and supplies. This includes rolls of red and blue PEX tubing (typically 1/2" for branches and 3/4" for main lines), a PEX manifold with enough ports for all your fixtures, a PEX clamp tool, a dedicated PEX tubing cutter, and a variety of PEX fittings such as elbows, tees, and couplings. You will also need PEX-to-copper transition fittings (like sweat-to-PEX adapters or push-to-connect fittings), PEX pipe clamps to secure the tubing, and new angle stop valves for each fixture.

Locate the main water shutoff valve for the house and turn it clockwise until it is fully closed. To drain the entire plumbing system, open all faucets, starting with the highest fixture in the house (e.g., an upstairs shower) and ending with the lowest (e.g., a basement sink or outdoor spigot). Let the water run until it stops. For safety, shut off the electrical breaker or the gas supply valve for your water heater. Place a bucket and towels under the water heater's drain valve and open it to drain the tank.

To access pipes hidden in walls and ceilings, you will need to cut into the drywall. Use a stud finder to locate studs, electrical wires, and other obstructions. Mark out clean, rectangular cutting lines with a pencil. Using a drywall saw or utility knife, carefully cut along these lines. Wearing safety glasses and a dust mask is essential to protect from dust and debris. Keep the cut-out pieces of drywall intact if possible, as they can be used to patch the holes later.

With the pipes exposed and the system drained, begin removing the old plumbing. Using a PEX tubing cutter (which also works well on polybutylene), cut the PB pipe into manageable sections and pull it out from the walls and crawlspaces. Wear work gloves to protect your hands. Be careful when disconnecting the old pipes from fixture valves and main lines to avoid causing damage.

Find a suitable location and use a drill to securely mount the new PEX manifold to a wall or backing board. Using a pipe cutter, cut the main hot and cold copper lines and install the PEX-to-copper transition fittings. Apply teflon tape to any threaded connections before tightening with a pipe wrench. Connect the manifold inlets to these transition fittings. Now, begin running the individual PEX lines. Pull a red PEX tube from the appropriate hot water port on the manifold to a hot water fixture location (e.g., kitchen sink hot side). Repeat with a blue PEX tube for the cold side. Continue this process for every fixture. As you run the tubing, use a drill and PEX pipe clamps to secure the tubing to joists or studs every 32-36 inches to prevent movement and noise.

At each fixture termination point, use the PEX tubing cutter to cut the PEX line to the desired length. Secure a PEX stub-out elbow or drop-ear elbow to the wall framing using a drill and screws. Slide a stainless steel PEX clamp ring onto the end of the PEX tube. Push the tube fully onto the barbed end of the elbow fitting. Slide the clamp ring over the barbed section, positioning it about 1/8" to 1/4" from the end of the tube. Squeeze the PEX clamp tool firmly until it clicks or fully closes, compressing the ring. Attach a new angle stop valve to the threaded end of the stub-out elbow. Repeat this for every hot and cold line at every fixture.

This is the moment of truth. Double-check that all angle stop valves at the fixtures are in the closed position and all valves on the PEX manifold are also closed. Go to your main water shutoff and turn it on VERY SLOWLY, just a quarter turn, to allow the pipes to fill with water gradually. Listen for the sound of rushing water to stop. Go inspect the main connections to the manifold for any leaks. If all is dry, slowly open the main valve the rest of the way. Then, one by one, open a single valve on the manifold. Meticulously inspect that entire line and its final connection for any drips. A dry paper towel wiped on each joint is a great way to detect tiny leaks. Once a line is confirmed to be dry, open the corresponding angle stop at the fixture to purge the air. Repeat this for every single line. Leave the system under full pressure for several hours (or overnight) before proceeding.

Once you are 100% confident the system is leak-free and it has passed any required inspections, you can begin the final restoration phase. Re-install the pieces of drywall you saved, securing them with drywall screws. Apply drywall tape over the seams and cover with several thin layers of joint compound, using taping knives for application. Allow each layer to dry completely. Sand the final layer smooth with a sander. Finally, apply a coat of primer, followed by a coat or two of paint to match the surrounding wall. Clean up all tools, dust, and debris from the work area.