What is this valve on the cold side of a water heater?

It has pressure markings on it. Is it what they used before expansion tanks?

Valve on water heater.jpg

A vacuum break.

Thank You. Just looked it up and some other sources cite a difference between a vacuum break and a vacuum relief valve. Is this an important distinction? Is the purpose to protect the water heater from dry firing after the fire department was active nearby? Aren’t there sensors in water heaters that would prevent this? Is this an unusual code requirement? Haven’t seen one before. Is this enough questions??? Ha!

Without looking it up, I believe they are useful for draining the tank.

It’s a vacuum breaker or “water service vacuum relief valve” and it is used to prevent water siphoning from the water heater. In Canada they must be installed on bottom feeded water heaters.


I thought that all WH are bottom feeded.

fed, not feeded. :mrgreen: