I need to replace a washer on my Delta faucet, but in simply trying to turn-off the cold water valve under the sink...it won't stop the cold water from coming out of the faucet. I could get the hot water valve turned off, but not the cold water valve.....any tricks to getting the cold Water valve to stop the water....I've tried turning it in and out several times, but it doesn't seem to ever stop the water totally like the hot side. The hot water valve worked perfectly....any ideas?