Mount the PEX manifold to the building at the end of the appropriate water-supply PEX pipe, using wood screws to hold the manifold in place. The manifold's intake port must face the water supply pipe. If the manifold controls the hot water supply, mount the manifold at the end of the water heater's discharge pipe. Run the wood screws through the manifold's mounting holes, using a Phillips screwdriver to turn the screws.
Slide a PEX crimp ring over the water-supply pipe. Position the crimp ring about 1/4-inch from the end of the pipe. Usually, a water-supply pipe uses 3/4-inch PEX pipe and a 3/4-inch crimp ring.
Push the water-supply pipe over the PEX manifold's intake port. Center the crimp ring between the two barbs on the manifold's intake port. Place the correct size PEX crimp tool on the crimp ring, holding the tool at a 90-degree angle to the manifold. Squeeze the crimp tool's handles until the jaws touch.
Slide the correctly sized PEX crimp ring over one of the PEX pipes leading to a plumbing fixture. Plumbing fixtures typically use either 1/4-, 3/8- or 1/2-inch PEX pipe and crimp rings. Push the PEX pipe onto one of the manifold's discharge ports. Adjust the crimp ring until it settles between the two barbs on the manifold port. Repeat this for each PEX pipe.
Position the correctly sized PEX crimp tool over a PEX crimp ring. Squeeze the crimp tool's handles until its jaws touch. Repeat this for each PEX pipe connection.
Slide a PEX pass/fail tool over each crimp ring. If the crimp ring slides into the pass/fail tool's "Pass" slot, the fitting passes inspection. If the crimp ring will not slide into the pass/fail tool's "Pass" slot, cut off the crimp ring with wire cutters and install a new crimp ring on the PEX pipe. A pass/fail tool has slots designed for each size of PEX pipe.
Run each PEX pipe connected to the manifold to its respective plumbing fixture. Leave a small amount of slack in the PEX pipes next to the manifold.