After having new shower put in my house I have a pinging noise coming from the pipes after a faucet is shut off. It happens with every facucet in the house and only after it is shut off. If I turn off the valve that supplies the hot water heater with water I do not hear it at all when I just run cold water. They replaced the valve and the hot water heater and still the echoing pinging noise.
Incidently when I turn off the hot water supply to the hot water heater I get cold coming out of every tap except the shower they replaced. I don't understand why I can't continue to get cold water out of the shower even though it is a single faucet.

Thanks to anyone and everyone.