I just bought a home and notice that the pressure is ok when I have one faucet running but when i flush the toilet or turn on another water source the water pressure drops. I am connected to a county water line and the water main is running thru my property. The house was built in 1975 and it does have a pressure regulator....it may have two if I am not mistaken. What could be some possible causes? Also the shower pressure isn't really all that great when it is running by itself. I need to change the shower fixtures and faucets as one of the shower knobs is stripped and water is dripping because it can't fully close. Thanks for any input.