anti siphon valve

larryeddington · Post by **larryeddington** » Sat Oct 29, 2011 11:31 pm

I am installing new aluminum fuel tanks and the subject of anti siphon valve came up. The original had shutoff valves at the tank and right before the fuel pumpl.

I think and correct me if I am wrong, an anti-siphon valve is supposed to block the flow fuel in case of a line break lower than the tank. As the fuel pump draws fuel from the tank how does a valve know the difference from a leak?

alexander38 · Post by **alexander38** » Sun Oct 30, 2011 4:40 am

your right Larry it's a must have for a gasser

koviak · Post by **koviak** » Sun Oct 30, 2011 7:28 am

Larry, your fuel pump is drawing thru valve with vacuum so the small spring and ball release to flow. If a line leaks without vacuum the valve will not open.

alexander38 · Post by **alexander38** » Sun Oct 30, 2011 7:47 am

koviak wrote:Larry, your fuel pump is drawing thru valve with vacuum so the small spring and ball release to flow. If a line leaks without vacuum the valve will not open.

sorry was still 1/2 a sleep...

Koviak is right on the money..

prowlersfish · Post by **prowlersfish** » Sun Oct 30, 2011 8:33 am

A leak wont have enough "pull" to open the valve . But you still should have cut off valve just in case .

larryeddington · Post by **larryeddington** » Sun Oct 30, 2011 9:39 am

Having a cutoff valve as well seems to be a good plan. My boat has copper fuel lines which I intend to retain. Presently the fuel exited the old galvanized tank via a cutoff valve and flared fitting on the copper line.

Seems like the only antisiphon valves I see are made with hose barbs for hoses. Is there one with threaded connection? I cannot locate one.

g36 · Post by **g36** » Sun Oct 30, 2011 6:32 pm

larry i replaced my tanks this year also and i did replace my antisiphon inline valves at the same time. i also reused my copper fuel lines but did install new antisiphons. if you will pm me i will be happy to give you the info on where i purchased them. these are the correct ones and not the barbed.