Water heater safety tank

[Scott Byrnes]

What is the purpose of the water heater safety tank on top of a water heater?

[phinsperger]

"Safety Tank"? It looks like a typical expansion tank. Used to allow a space for water to go when heated and expands.

[David P. Valley]

That is an expansion tank.

The main purpose of the expansion tank is to compenate for the expansion of water due to heating it against a closed valve, check valve, or backflow preventor upstream of the water heater.

This expansion tank will basically give expanding hot water a place to go so the increase in pressure brought about by heating the water will be controlled and not cause a failure in the plumbing system. There'a a bladder in this tank that expands as pressured hot water enters, then the water recycles itself back into the plumbing system as it cools down.

[Scott Byrnes]

I figured it was an expansion tank, but I also figured it never hurts to verify. Thanks guys! It's good to be NACHI