Anti Siphon Valve on Fuel Tank Pickup?

[Captain Jeff]

I have a 1999 Angler center console with a Johnson 115 and a 40 gallon fuel tank below deck. I am replacing all the fuel lines, sender and fuel pickup tube. I bought a Seachoice Anti-Siphon Valve, 1/4 in. NPT, 3/8 in.

Technically I don't think I need it per USCG regulations because the hose is above the level of the tank top. Is it good to have it anyway or do people have a lot of issues with anti siphon valves? Thank You

 

[oldboat1]

Think the bulb serves as an anti siphon valve, along with the fuel connector at the motor.

 

[Chris1956]

The primer bulb and the fuel line connector DO NOT serve as an anti siphon valve. The A-S valve shuts off the fuel, if the fuel line breaks at a place lower then the fuel level in the tank. if it does that, fuel would siphon into the boat bilge.

If your fuel line never dips below the fuel level in the tank, and can never do so, you may not need an A-S valve. Most built in tanks cannot claim that.

 

[dingbat]

Took the anti-siphon off mine and threw it away 15 years ago.

Anti-Siphon valves……brought to you by the same people who think mounting an internal combustion motor(s) and tank(s) of highly flammable fuel in the same confined space is a good idea..then throw the batteries in the same space for good luck.

What possibly could go wrong…lol

 

[oldboat1]

Years ago I had a '54 Trojan Sea Breeze outboard cruiser (21') running copper lines from the two saddle tanks to the selector switch in the stern, along with the bulb and rubber hoses in the motor well. One solution may be to replace lines under the floor with copper. Anti-siphon valves can fail, stalling the engine. If you have one, it should be checked if you have any operating problems related to fuel feed.

 

[Chris1956]

Well that explains why you call yourself dingbat. It is a good thing your fuel lines have lasted 15 years, without leaking fuel into the bilge.

 

[dingbat]

Well that explains why you call yourself dingbat. It is a good thing your fuel lines have lasted 15 years, without leaking fuel into the bilge.

Perhaps our resident physics Professor Chris1956 could explain to us how to siphon liquids uphill…..lol

BTW here is the regulation…
I choose option (a) as I’m outboard powered. Option (b) applies to industrial egg beaters mounted in a hazardous locations.

§ 183.568 Anti-siphon protection.
Each fuel line from the fuel tank to the fuel inlet connection on the carburetor must:

(a) Be above the level of the tank top; or

(b) Have an anti-siphon device or an electrically operated fuelstop valve:

 

[Chris1956]

Dingbat, as long as your fuel line never dips below the top of the tank, even if it breaks, you will have no issue. Not sure your reference is complete

However, most below deck tanks have a flexible fuel line that runs under the deck to the transom area, and then up to the engine or a filter. These usually are routed down a bit either by design, say to fit thru a pipe passage, or by drooping.

if the fuel line breaks, the broken end can fall down, below the tank, and as it is full of fuel, a siphon can occur. Your engine will eventually stall, as fuel pours into your bilge. Actually, the fuel line doesn't even need to break, A simple hole from rubbing against the hull, causing a leak will cause a siphon effect, if in the wrong place.

The only way Option (a) applies is if the fuel lines run directly up from the fuel tank to the engine, will not get a hole in it, and cannot break and fall down under gravity. Rigid fuel lines might satisfy this. If that is what you have, you are exempt. If not you have the "custom bomb" style fuel system.

See no professorship needed.

Some regulations make sense. Blowers in inboard gasoline powered boats were required since 1940. A good idea then, still a good one.