A: Gas water heaters when turned low will form condensation in the burning chamber of the heater and will make for puddles of water. In fact, many people suspect their heater has a leak when this occurs. If you are sure that it is coming from the relief valve then it is overpressure in the system at certain times caused by heating and cooling of the heater and that the water company puts back flow preventers on your system. Thus, when the heater is not in use and cools, it draws in cold water as the water in the heater contracts. When the unit comes on and heats the water, the water expands and since no one is there to use the water it creats an overpressure which forces water out of the relief valve rather then rupturing your heater. This can be prevented by putting in a small expansion tank. We sell ones that require no tools and are easy to install if you want. If it is condensation, you can either turn the heater off, or leave it at the full temp.