I'm trying to replace kitchen faucet, cannot get the hotwater oval shutoff valve to close completely -water still comes thru the faucet. it seems to be as tight as it can get without forcing it. There is no other shutoff prior to the kitchen sink. I read where I should shut off the main line to the house when this happens, but how will that keep the hotwater faucet from draining the hotwater heater? or is that ok?