Our cold water faucets always produce an initial stream of hot water before
the cold starts. I believe it has to do with the expansion tank on the
heater. There is a check valve on the water line that feeds the heater, but
the backflow seems to indicate that it does not work. It is the flapper
type and it is pointed down. Is there a problem with trying to use this
sort of check valve in a downward position? I checked the arrow marking and
it appears to be installed in the right direction.