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Anti-Sephon Valve Leaks

Hi, Experts,

I have anti-sephon valves on the outlet water taps in the outside of house.

Now it is leaking from one of small holes on the sephon valve (it is designed that way or about 12 holes were designed & machined there) I think. It leaks or splashes through the small hole when I turn the tap on.

In fact, It went out to leak or splash one day (hot day) by itself. Fortunately I was nearby and turned it off.

My question is:

Is it repairable? is it hard to replace the entire tape/sephon valve with it? I have never done it. Please teach me how.

Thanks a lot,


A. Spruce
Re: Anti-Sephon Valve Leaks

Doesn't really sound like there's a problem with it to me. The purpose of an anti-siphon valve is to prevent back pressure in the hose forcing possible contaminated water into the house system.

Basically, it's a one way diaphragm. House water is able to pass, but not return. If you had the hose on, laying in the sun, the water expands and increases pressure, resulting in a drip at the valve. Similarly, if you drive over that hose, the weight of the car will pressurize the hose and water will drip/squirt out. Turn off the house pressure and the valve releases the hose pressure which usually results in a nice cold shower for whomever is standing nearby.

If you've got a constant drip at that faucet without the hosebib being on, then the hosebib itself is leaking and either needs to be rebuilt or replaced.

Re: Anti-Sephon Valve Leaks

I'm having a similar problem. With a hose attached, water pours out of my anti-siphon valve when the water's turned one. I open the hose, water trickles out of the hose but still pours out of the anti-siphon valve. I would think the valve is stuck open (grit, or whatever) but if I disconnect the hose, the faucet operates normally with nothing coming out of the anti-siphon value. Any ideas about why this is happening?


A. Spruce
Re: Anti-Sephon Valve Leaks

Sounds like the anti-siphon if either damaged or broken, it happens. Replace the anti-siphon. New units should be in the hose bib section of the hardware supply. There is usually a set screw that binds the anti-siphon to the hose bib, loosen the screw before trying to unscrew the unit. If that doesn't work you can replace the whole hose bib easily enough.

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