Made of cross-linked polythene, PEX pipe is flexible and, unlike conventional CPVC and cooper water pipes, requires no cement or solder to join sections together. The PEX pipe sections, once cut to length, join together with barbed male-ended fittings and crimp rings. You can install the plastic or brass fittings more than once. Repairing a pinhole leak in a PEX pipe section requires cutting out the leak and installing a new PEX pipe section in its place. PEX fittings join the existing pipe to the new pipe.
Turn the water supply off at the home's main shutoff valve. Measure 15 cm (6 inches) from each side of the pinhole leak on each section of pipe using a tape measure, and mark these spots with a marker pen. Place the pipe into the jaws of a PEX tube cutter, resting the cutter's sharp jaw blade on the mark, and at 90 degrees to the pipe. Squeeze the cutter's handles together to make a straight, clean, perpendicular cut through the pipe. Cut though the pipe at the second mark following the same process.
Slip a copper crimp ring onto each of the existing pipe ends, sliding the rings 7.5 cm (3 inches) along the pipes. Push a straight PEX fitting into the end of each pipe so each pipe end meets the fitting's shoulder. Slide each crimp ring toward the fitting, leaving a 3 mm (1/8 inch) gap between the ring and the fitting's shoulder.
Place one of the crimp rings in the jaws of a crimp ring tool with the tool's handles open and the tool perpendicular to the pipe. Close the tool's handles to squeeze and seal the crimp ring in place. Repeat this process with the second crimp ring.
Slip each installed crimp ring into both slots on a "go/no go" gauge; the rings should slip into the "go" slot but not the "no go" slot. If either crimp ring fails the test, remove and reinstall it.
Measure between the shoulders of the installed PEX fittings, and cut a section of PEX pipe to that length. Check to ensure the new PEX pipe has the same diameter as the existing pipe. Follow the same installation procedure as described to attach and fit the new pipe section to the remaining barbed ends of the two fittings using crimp rings, the crimp tool and "go/no go" gauge. Turn on the water supply.
PEX pipe comes in 9 mm, 1.2 cm, 1.5 cm, 1.8 cm and 2.5 (3/8, 1/2, 5/8, 3/4 and 1 inch) diameters.