on demand hot water heater for years and it worked great. Hot water as often and as long as you had water. The only problem I had was in Jamaica when the fool filling it told me he was filling the tank with propane but it was butane. I took the tank back to the boat and when I fired off the water heater I had a ball of fire that you wouldn't believe. I shut down the water heater by closing the sink valve and the fire went out so all was well. I went back to where I had it filled and he said "propane, butane, all de same ting, mon". Just watch what they put in your tank! Most of the on demand heaters are installed in a locker but mine was installed on the bulkhead in the head. It was a good thing because I don't know what would have happened if it had been in a confined space.