Mother has CPVC in the attic. We turned the water off when the freeze started. Wondered a way to test pipes before flowing water and causing damage. A plumber friend showed me how to make a device. garden hose fitting and air hose. Close all valves in the house including the commode. Go outside and connect to the water faucet where you normally connect your garden hose. Pressure up with compressor, to about 60 pounds and if no drop your good. If drop leave compressor run and start listening for air leak.