Husband installed hot water heater last Dec. Now when we run water anywhere, pipes shriek like I'm murdering him (I'm about to!). If we turn on another faucet, it stops. Three times we've turned on all faucets and flushed then turned water off at the main. After pipes run dry, closed faucets and turned water back on to house. Shrieking went away for a few days, then over the course of a few days, returns. Louder and LOUDer and LOUDER.
Other than spirits of the undead, what could be causing this?