alt.energy.homepower

-> >> Some states is the US also require a gas water heater to be equipped
-> >> with a "vacuum breaker" valve on the water feed line, which allow air
-> >> to enter the tank if a negative pressure were to develop in the water
-> >> supply line. This can happen if a fire developes in the neighborhood,
-> >> and the fire department is heavily pumping from nearby fire hydrants.
-> >
-> > An anti-vacuum valve can be anywhere on the tank. Why on the incoming cold
-> > mains pipe?
-> I would think it's to prevent siphoning of water from any part of the
-> househould plumbing back into the municipal supply lines.

-> Don Young

We wouldn't want our water to be sucked out and used for fighting
someone else's fire, would we?

dow