Fuel line siphon prevention?

[Cyrus Safdari]

Reading thru old Marine acc8dent investigation reports
Came across a point I never thought about
How do you stop siphon effect if there is a leak on a fuel pump located below fuel tank? >link<

[Cyrus Safdari]

Could someone explain what a fuel line anti siphon valve is and why I don't see references to one in usual boating diy sources?
https://marinepartssource.com/anti-s...-a-s-l-170-1-2
Looks like a stnd hose to barb adaptor

I am trying to install a fuel line emergency shut off valve using a stnd 3/8 mnpt pickup
They make shutoff valves in brass a plenty like Kantleak UL-listed ones also made by racor and whitecap

Has anyone ever used one of these spring loaded shutoff valves? Just a tug trips it

https://www.seascrew.com/browse.cfm?...P&p=0000006068

[mlydon]

Most tanks I’ve seen (but not all) have a stopcock right at the pickup tube. Brass is just fine for fuel.
Something like you posted is only useful if you are present, and notice the leak, to trip the valve - by all mess, feel free, but not a very common problem.

What type engine?

Mat

[Cyrus Safdari]

Yes for comm vessels a shutoff at pickup is reqd manually operated too, makes perfect sense for non comm vessels like any sailboat with a fuel tank best if remotely operated by wire so you can quickly turn off fuel in case of a disaster rather than bilge full of fuel and huge fines. If getting a fuel shutoff - which is kinda something you'd reasonably expect to have - , heck why not a spring loaded one designed for the purpose operated from someplace convenient? It doesn't have to be fancy,, a simple wire tied to the handle routed somewhere saying helm area, just about an inch or two tug to shut off fuel
In case of a fire who is going to crawl down into where ever the tank is to turn off fuel?
They also make spring loaded ball valves in bronze I guess point is quick (remote) activation too
One more shutoff is needed before fuel filter, for when replacing the filter
But I'm more curious about the antisiphon valve in the link, some store descriptions says something about it being federally reqd ? It looks like a plain hose adaptor. How does it even work? Is there a pinhole? Tube within a tube? How does it prevent siphoning in case of fuel pump failure exactly because that implies a vent going before a pump which generally doesn't work
If there should be a leak in fuel line, and there is a cheapest product that prevents it somehow I'd sure like to know about it as unlikely it may be to happen.

[HopCar]

The anti siphon valves are just check valves. The spring is weak enough that fuel pumps can pull fuel through them but strong enough to break a siphon.
I think the ABYC requires them on gasoline tanks. I had them on my diesel tanks but not sure if they were required.

[Cyrus Safdari]

Wow thank you
This seems like a reasonable thing to have on a diesel vessel too esp since the cost is minimal. Is there any technical or practical or safety downside to using one for diesel tanks?

I certainly would not want gasoline siphoning out of a fuel tank aboard, but pretty much the same goes for diesel even if it is not as explosive. The environmental fees for a spill alone...!

I'm not clear on how they're installed. They're screwed straight into the standard 3/8 pickup on one side and the fuel hose on the other?
(after a valve?) Do they have to be in any direction?

[HopCar]

“ I'm not clear on how they're installed. They're screwed straight into the standard 3/8 pickup on one side and the fuel hose on the other?”

It just screws into the top of the pickup tube. You could put a shutoff valve between the anti siphon valve and the pickup tube but I don’t see any reason to do that.

[mlydon]

Diesel bugs that end up in your filter cold conceivably glue it closed…..

Matt

[Cyrus Safdari]

Thank you all
I will have shutoffs for sure, if only to be able to work on the fuel line if needed

Is there an issue of galvznic reaction in using brass fittings on aluminum tanks?

[HopCar]

Originally Posted by Cyrus Safdari

Is there an issue of galvznic reaction in using brass fittings on aluminum tanks?

Yes, don’t use brass in contact with aluminum.