Replacing dishwasher. Three way (hot water line, sink faucet, dishwasher) valve on hot water supply is off. There is a single handle faucet on sink. Cold water valve still on. I have unhooked the water supply from dishwasher and laying on floor--little water came out. However I later found large puddle after wife used the sink cold water. Then I put end of water line up at sink level and low and behold, when cold water turned on there was some squirt out of the hot water line. I now assume that turning the valve off stops off the hot water supply but the two supply holes and tubes are not blocked off by the valve??? so I am getting water from the faucet cold water pushing/siphoning back down the hot water line? Is this reasonable or could it be a faulty hot water line valve. Dont want to replace a valve if its not the reason. Thanx for help/info