If the water is already hot (from electric heating), the gas element won't come on since there is no need for extra heat. Both the electric and the gas heaters are on thermostats, and the thermostats don't have exactly identical settings. Sounds to me like your electric heater is set slightly higher than your gas element, so it kicks in earlier, and the gas never sees the need to come on.
Turn off the electric heater, and see if the gas keeps it hot.
Bill
|