My water heater tank started leaking and while draining it I noticed there is cold water backflowing through the supply line. So I most likely have a valve somewhere that is letting cold water into the hot water line. I believe I know which one is the culprit. I don't believe the situation is easily fixable, but I won't go into that here and now.
Can I just put a check valve in the hot water line line coming out of the water heater when I install the new one? Is there any safety issue with doing this?
I would appreciate any good advice.