One option to consider. If the plumbing from the water heater to the
upstairs sink goes up, or horizontal with no "down" dips, then it is
possible the hot water is migrating up by convection.

I know that in several applications I've worked on, the installer has
deliberately put in a dip (somewhat like a J-trap under a sink) to prevent
hot from migrating up the pipes.

The other posters are also correct, you may have a small leak. Check around.
If you don't have a small leak, then you very possibly have natural
convection going on. If that's the case, just smile a big grin, and enjoy
it.

--

Christopher A. Young
Jesus: The Reason for the Season
www.lds.org
www.mormons.com


"TigerPaw40" wrote in message
...
Moved into a 1978 built two story home. The weird thing is we get instant
hot
water upstairs in both bathrooms. In all the homes I have lived in you would
have to run the water a bit to get hot water. In this house the water is
very
hot instantly. Is this something that was designed in the home, or could I
have
some type of plumbing problem?