I should add that the water heater is not in the basement; it's on the first floor. I understand that if it were in the basement (below all the rest of the hot water pipes), there would be some recirculation because of the difference in density between hot and cold water. In my house, most of the tank is actually higher than the rest of the system, and that probably makes the hot water want to go back into the tank rather than stay in the pipes.

MC wrote:
I should add that the water heater is not in the basement; it's on the first floor. I understand that if it were in the basement (below all the rest of the hot water pipes), there would be some recirculation because of the difference in density between hot and cold water. In my house, most of the tank is actually higher than the rest of the system, and that probably makes the hot water want to go back into the tank rather than stay in the pipes.



Is the piping exposed?
If so, the first step should be to insulate the entire run.

Jim