Polybutylene pipes were once used in homes for water supply lines. Today, many problematic issues have forced building regulation to stop allowing this type of pipe to be installed. If a shut-off valve is faulty on an existing polybutylene pipeline, short of replacing the entire pipeline, the valve can be cut out of the line and replaced with a CPVC shut-off valve. CPVC pipe attaches to each side of the valve, which in turn connects to the polybutylene pipe with adaptor couplings.
Turn off the main water supply to the house at the shut-off valve.
Drain the pipes by turning on the lowest faucet in the house.
Mark the polybutylene pipe 6 inches on each side of the problematic valve.
Make a clean straight cut through the pipe at both marks using a tube cutter, and remove the old valve.
Unscrew and remove the nuts on both ends of two adaptor couplings, followed by the steel crimp fittings and acetal compression sleeves found between the coupling body and end nuts.
Slide a nut on the end of each cut pipe, and slip a crimp fitting on each pipe end, followed by the compression sleeve.
Cut two pieces of CPVC pipe 8 inches or longer using the tube cutter.
Brush PVC primer to one outside end of both pipes, as well as both inlets on a CPVC shut-off valve.
Brush PVC cement onto all four primed areas.
Push the cemented ends of the pipes into the inlets on each end of the valve, and hold in place for 10 seconds while the cements sets.
Hold the valves and CPVC pipes in place against the existing polybutylene pipes.
Mark each CPVC pipe at the point where it will connect to the adaptor coupling (allow for how much each CPVC pipe will enter into the coupling body).
Cut the CPVC pipes at the marks using the tube cutter.
Slide the adaptor coupling's remaining nuts onto the ends of the CPVC pipes, followed by the crimp fittings and acetal compression sleeves.
Squeeze the end of the CPVC pipes into each adaptor coupling body.
Screw the nuts onto each adaptor coupling, and tighten them in place with the crescent wrench.
Turn the water back on, and open the CPVC shut-off valve.
Some CPVC shut-off valves have a nut on each end and do not require primer or cement. They are merely pushed onto the CPVC pipe ends and the nuts, then tightened in place.