Auto Shut-Off Feature for Safety

No one wants a water heater to “just stop working,” but sometimes it’s a good for everything to shut down.

Two shutoff types 

There are a couple of different auto-shut off features available in standard water heaters.


For example, if the pilot light on a natural gas commercial water heater or a propane commercial water heater goes out, it’s best that the gas source also be shut off for health and safety reasons.


Another good time for functions on water heaters to shut off is if there’s a water leak or some other plumbing problem. Devices can be purchased that will automatically shut off the water supply, thus saving the water heater from damaging corrosion and saving the home from water damage, both of which would be caused from the ensuing floods if the water is not shut off from the water heater.


Pilot Light Goes “Unlit”? 

Pilot lights sometimes go out and having an auto-shut off feature that turns off the gas is important in case this happens.

Auto-shutoff devices for water generally have to be purchased separately as an accessory and are usually used for residential purposes.


Auto-shut off features for when the pilot light gets extinguished come in most commercial natural gas water heaters and commercial propane water heaters. Our Rheem and AO Smith commercial water heaters that are powered by natural gas or propane come with this safety feature, which is listed in the product descriptions on The safety cut-off switch senses when the pilot light goes out and shuts off the gas or propane so that the home or commercial business is not filled with unburned natural gas or propane. If this happens, it creates an explosion risk and a threat to health for humans and animals.


Why would a pilot light go out? There are several possible reasons, but the most likely cause is improper venting. Other reasons include capping, high ambient temperature, decompression or a faulty pilot light unit.


How does it know?


The cut-off switch usually detects the pilot light in one of three ways:

  • A mercury-filled sensor detects the pilot light’s heat. The contracting mercury decreases the pressure that is required to operate the electric switch, which then interrupts the water heater’s electricity flow and that shuts off the gas valve.
  • A device called a photoresistor is used to detect light from the pilot light. When the pilot light gets extinguished, obviously it is not producing light, which leads the photoresistor to shut off the gas valve.
  • Use of a pilot generator or thermocouple in the flame generates enough electricity from the burning pilot light flame to hold the gas valve open. When the pilot light goes out, the current is stopped because it no longer has that heat source. When the current stops, the gas valve shuts.


Need help? 

As always, the staff at is here to help you with the information and products you need for electric, natural gaspropanetanklessexpansion and booster water heaters.