Anti-siphon valve

[Aviator5]

What is it's purpose, beside restricting fuel flow and catching some junk. I had problems with this valve on 2 different boats. This time it didn't even work, the ball was stuck inside the spring, and piese of junk got stuck there too. I went to local marina and asked for replacement and the mechanic advised to pop that ball out completely or use a regular barb fitting without the valve, that is what thay do, he said. So what that valve is supposed to do anyways?
Thank you everybody.

 

[familyguy]

Re: Anti-siphon valve

Keeps fuel from leaking out of the fitting/line in the event there is some kind of accident that causes the line to get disconnected. However, if the same accident causes the fill or vent hose to be disconnected the antisiphon valve is useless.​

 

[Zackman]

Re: Anti-siphon valve

Also a CG regulation... See section 183.568 here http://edocket.access.gpo.gov/cfr_2008/julqtr/pdf/33cfr183.568.pdf

Additionally, they are really cheap insurance. ​

 

[Bt Doctur]

Re: Anti-siphon valve

A manual shut-off valve at the tank is also ok.

 

[Don S]

Re: Anti-siphon valve

A manual shut-off valve at the tank is also ok.

While it is legal, it does not work automatically like the anti siphon valve to stop the flow of fuel in case of an emergency. If a fire were to start, you could need to reach into a fire to shut the manual valve off.

If your tank is so dirty that it keeps plugging up antisiphon valves, then you really need to clean your tank, not get rid of the safety feature.

Keeps fuel from leaking out of the fitting/line in the event there is some kind of accident that causes the line to get disconnected. However, if the same accident causes the fill or vent hose to be disconnected the antisiphon valve is useless.

1. It's not there to prevent leakage, it's there to stop fuel from siphoing out of the tank incase a line breaks or burns through BELOW the level of the fuel.
It stops the fuel from siphoning out of the tank, not leaking out.
The fuel pickup goes to the bottom of the tank t o pick up fuel. The vent and fill hoses are at the top of the tank and do not extend into the tank.

Amazing how many people don't have a clue how a tank is made or works, and why things are the way the are.

 

[Big Keepers]

Re: Anti-siphon valve

I put a manual shutoff on my tank since my fuel line never dips below the top level of the tank, it is always above it. Of course I have a 20' boat and can reach any part of it in two seconds. On larger boats with buried hoses and dips in the line an anti-siphon valve is better than a manual shutoff. As was stated if you're valve is constantly being clogged your tank is in need of a cleaning.

 

[familyguy]

Re: Anti-siphon valve

Amazing how many people don't have a clue how a tank is made or works, and why things are the way the are.

Actually Don, I have a bit of a clue seeing as how I personally completely dismantled my fuel delivery system including tank removal, pressure test, and reinstallation.​

I am certainly no expert on boat and engine repair as I know you are by virtue of your posting quality, and I mean that in a serious, not sarcastic way, but I am learning to know my boat and on mine there aren't even any fuel lines below the level of the fuel like Big Keepers mentioned. I'm not sure how the fuel could siphon out without an antisiphon valve unless the fuel pump supply line was pushed down into the bottom of the bilge after it became disconnected.​

If that occurred in an accident/collision/fire/whathaveyou then the fill and vent hoses could become disconnected/burn/break as well by nature of the force necessary to cause that supply hose to become loose/break/burn therefore leading to the same problem: fuel leakage/siphoning/spillage...danger.​

I agree with you and Big Keepers that Aviator5 should probably pull his tank and make sure it doesn't have a bunch of debris in it.​

Seriously though Don, thank you for all your postings. I've learned a lot through you sharing repair info.​