How come water heaters dont need a low water cutoff?

RayWohlfarth

I was doing research for a video and wondered why water heaters dont need a low water cutoff. I asked AI and it said its because they have city water pressure all the time but I have seen water heaters with valve on both supply and return, Maybe its because the building is filled with water Just curious

Ray

EdTheHeaterMan

Just about every code requirement exists because of an insurance claim or some other catastrophic occurrence where lives were lost, people were injured, or property was damaged.

Low-water cutoff devices became required on boilers because boilers contain a relatively large volume of water and operate at high temperatures and pressures. If a boiler is fired without water in it, the metal can overheat and fail violently when water is reintroduced. Historically, those failures caused serious explosions and fatalities, which led to the requirement for LWCO devices in boiler codes.

So the short answer is that codes usually follow accidents and insurance losses, and there has not been the same history of catastrophic failures from dry-fired water heaters that would justify requiring a low-water cutoff on them.

ChrisJ

https://forum.heatinghelp.com/discussion/204219/how-come-water-heaters-dont-need-a-low-water-cutoff

Tank heaters are controlled by a thermostat that's mounted almost at the bottom of the tank. If the tank runs very low on water that thermostat is still controlling it, and I'd bet 99.9% of the time long before it would ever lose any amount of water someone will be down there inspecting it because they have no hot water.

I guess somehow, the water supply could be shutoff and the bottom drain could bust off at the same time, but that seems really unrealistic.

Larry Weingarten

Hi, One of the safeties built into tank-type heaters most people don't know about is the little hole towards the top of the dip tube, (which delivers water to the bottom of the tank from the top connection). I've found this vacuum breaker (sometimes called the sneft hole) prevents water from being siphoned from the tank in the event of loss of water pressure AND a water leak downstream of the tank. With this, the tank usually stays mostly full of water, which is safer.

Yours, Larry

hot_rod

The ECO energy cut off is built into the gas valve. From AO Smith

And snap discs on electric tanks

RayWohlfarth

Thanks for answering that burning question. Always wondered Have a great weekend everyone