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Posted by Don Young on September 6, 2007, 9:36 pm
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>-> >> 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
I think the concern is possible contamination of the municipal water supply
lines from anything introduced into the household plumbing. There are quite
a few cross connection, air gap, check valve, vacuum breaker, and
anti-siphon regulations to help prevent this. I make no judgements as to
whether said regulations are necessary or worthwhile.
Don Young
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