Reply To: Cold retroflow in hot water lines

: I have a wye fitting that opens both hot and cold taps to join at a common hose. If the taps are left open, even though the hose outlet it closed, I will only get lukewarm water at the other hot water taps in the building. In other words the cold water flows back into the hot water lines. Why is that? the reason being that it,s easier for the water to short cycle through the y than go through hot pipe only.you need a check valve on each pipe before the y.