Recently we had an electrical power outage and the pilot lights on our hot water heaters went out. What is the rational for setting these things to go out when electricity goes out. I was thinking perhaps it’s because the exhaust fan stops working, but it seems that the pilot flame is akin to a candle and that danger of CO poisoning seems inconceivable at best. The heater does have an manual restart, if that makes any difference.
I can’t answer your question, but can say that I don’t think this is standard behavior. The pilot in my hot water heater doesn’t go out when the power is off. Does yours also have a relay on the pilot light gas supply so it’s not still trickling gas when the pilot is out? I suppose it does since this would be the most logical way to safely extinguish the pilot when the power fails (if you wanted that to happen). On mine, if the pilot is out I have to manually turn the gas supply valve to shut off the flow to the pilot. Mine is ~5 years old, so newer ones may have smarter controls.
Perhaps you have a electric pilot instead of a flame. Many newer gas appliances have these, which use an electric spark to ignite when needed instead of an always-on pilot light flame. My gas furnace uses these, and it makes sense to disable the furnace when the power is out since the distribution blowers won’t work anyway, but disabling hot water when the power is out seems like adding insult to injury.
Chance are, if a modern appliance, there is no pilot light. It’s electric start.
A cabin I use in the mountains has this situation. The propane-powered water heater is in the stand-up crawl space. When the electricity fails, which happens often in winter and spring, there is no power to run an exhaust fan that vents combustion gases from the water heater.
Building code says that if there is no exhaust fan for that type of installation, then the water heater must not work. A solenoid valve closes and cuts off the gas supply to the entire water heater. The code specifies this cutoff for any combustion-powered water heater, regardless of whether it has a pilot light or electronic ignition. It’s not the pilot light that could produce significant toxic products. It’s the main burner.
The fact that the water heater runs on propane instead of methane is not signifiant in this discussion. I’m sure that it’s the water heater locations that causes the code requirement. As you might guess, a small uninterruptible power source (UPS) just like I have on my computer and my VCR will keep the water heater alive through short power outages. (Power is only needed to run the exhaust fan when the burner is burning, which isn’t often except around meal and bath times.) If the power outage is longer, then the UPS goes dead and the solenoid cuts off, as required.
Never would I have thought I would install a UPS for a gas water heater.