The first and most critical step is to create a detailed plan and obtain the necessary permits. Begin by drawing a schematic of your home's plumbing system. Identify the location of every fixture (sinks, toilets, showers, washing machine, etc.), noting both hot and cold water lines. Decide on a central, accessible location for the PEX manifold, such as a utility room or basement wall. Plan the route for each PEX line from the manifold to its respective fixture, aiming for the most direct path with the fewest bends. Based on this plan, create a comprehensive materials list including the total footage of 1/2-inch and 3/4-inch PEX tubing, the number and types of fittings (elbows, tees, adapters), valves, pipe hangers, and the manifold itself. With your plan in hand, contact your local building department to apply for a plumbing permit. Do not begin work until the permit is approved.

Before any pipes are cut, you must completely shut off and drain the water system. Locate your home's main water shutoff valve, which is typically found where the water service line enters the house, near the water meter, or at the street in a utility box. Turn the valve clockwise until it is fully closed. Next, open every faucet in the house, both hot and cold, starting with the highest fixture (e.g., an upstairs shower) and ending with the lowest (e.g., a basement sink or outdoor spigot). This allows air to enter the system and ensures all water drains out. Flush all toilets to empty their tanks and cisterns. Connect a garden hose to a low-point drain valve or spigot to direct the remaining water outside or into a floor drain.

To replace the pipes, you must first access them. Use a stud finder to locate the wall studs on either side of where the pipes run. This allows you to make clean cuts and provides a solid surface for reattaching the drywall later. Using a drywall saw or utility knife, carefully cut rectangular sections of drywall to expose the polybutylene pipes. Make your cuts neat and try to save the removed pieces. Be extremely cautious of any electrical wiring or other utilities that may be hidden in the wall cavities. Wear safety glasses and a dust mask to protect yourself from dust and debris.

With the pipes exposed, begin removing the old polybutylene system. Wear gloves and safety glasses. It is often easiest to start at the fixtures and work your way back toward the main supply lines. Use a PEX/tubing cutter to cut the grey PB pipe into manageable sections for easy removal. The pipe and its plastic fittings can be very brittle, so expect them to crack or break. Disconnect the pipes from the fixture shutoff valves (these will also be replaced). Carefully pull the old pipes out from the wall and ceiling cavities. Keep a bucket handy to catch any remaining water.

Select a suitable location for your new PEX manifold, ensuring it is accessible for future maintenance. Mount a piece of 3/4-inch plywood to the wall studs to create a solid backing board. Use a level to position the manifold on the plywood and secure it firmly with screws. The manifold will have a main inlet for the hot water supply and another for the cold. Each fixture in your house will have its own dedicated port on both the hot and cold sides of the manifold, each controlled by a small ball valve.

Now it's time to run the new PEX lines. Use blue PEX for cold water and red PEX for hot water to maintain clear identification. Starting at the manifold, unroll and run a continuous PEX line to each fixture location. You can often follow the same paths as the old pipes. If you need to drill new holes through studs or joists, use an auger or spade bit and keep the holes centered to avoid accidental piercing with future nails or screws. To prevent sagging and water hammer noise, secure the PEX tubing with plastic pipe hangers every 32 inches on horizontal runs and every 48 inches on vertical runs. PEX is flexible, so use wide, sweeping turns instead of sharp 90-degree fittings where possible.

At each fixture and at the manifold, you will make your connections. Start by cutting the PEX pipe to the desired length with a PEX cutter, ensuring the cut is perfectly square and clean. Slide a copper crimp ring over the end of the pipe. Fully insert the barbed end of the PEX fitting (e.g., a drop-ear elbow for a shower head or an angle stop for a sink) into the pipe until it seats against the shoulder of the fitting. Position the copper crimp ring so it is 1/8 to 1/4 inch from the end of the pipe, covering the barbed section. Squeeze the handles of the PEX crimp tool completely to compress the ring. Finally, use a go/no-go gauge to verify the crimp's diameter; the 'go' slot should fit over the ring, but the 'no-go' slot should not.

This is the final plumbing step: connecting your new system to the water source. Ensure the main shutoff valve is still closed. Use a tubing cutter to make a clean cut on the main copper supply line after the shutoff valve. Clean and deburr the cut end of the copper pipe. Connect the main line to the hot and cold inlets of your PEX manifold. This is typically done using PEX-to-copper transition fittings. Push-to-connect fittings are a popular DIY option, or you can use PEX-to-copper sweat adapters if you are comfortable soldering. Repeat this process for the hot water outlet from your water heater, connecting it to the hot water inlet on the manifold.

Before closing the walls, you must thoroughly test the new system for leaks. Double-check that all fixture shutoff valves and all individual ports on the manifold are in the closed position. Go to the main water shutoff valve and open it only about a quarter of the way. This allows the pipes to fill with water slowly, preventing a sudden pressure surge (water hammer) that could damage fittings. Listen for the sound of running water to stop, indicating the system is full. Then, fully open the main valve. With the system under full pressure, meticulously inspect every single connection you made. Use a flashlight and a dry paper towel to wipe each fitting and check for even the smallest amount of moisture. Let the system remain under pressure for several hours (or as required by your permit inspector) and perform another thorough inspection.

Once you are completely confident that the system is leak-free and has passed any required inspections, you can begin the final phase of the project. If you removed any insulation, replace it now. Re-install the pieces of drywall you carefully cut out earlier, securing them to the studs with drywall screws. Apply drywall tape over all the seams. Using a taping knife, apply several thin coats of joint compound over the tape, feathering the edges to blend with the existing wall. Allow each coat to dry completely and sand it smooth before applying the next. Once the final coat is sanded and smooth, apply a coat of primer, followed by a top coat of paint that matches the rest of the wall.