Does anyone happen to know the thread size for the anti-siphon valve on a 2003 Seafarer 228? I am going to replace mine. I know the barb is 3/8 inch, but not sure the specs for the threaded portion. It will likely be "something" NPT, but I don't know what the "something thread size/pitch is. Thanks.
Anti Siphon Valve
- Thread starter jbsman099
- Start date
I think they're pretty much all the same, aren't they? Probably 1/4".
Are you sure it's bad? Spray it with some brakleen and shake it around and clean it out.
Are you sure it's bad? Spray it with some brakleen and shake it around and clean it out.
There is a 3/8 x 1/4 NPT, a 3/8 x 3/8 NPT and others. The outside thread diameter on mine looks to be around 5/8" (although that is just a guess, didn't measure it yet). My valve seems to have some debris in it I cannot get out. It also allows fuel to drain fairly quickly back into the tank when the line is open. It being 19 years old, I'd just as soon replace it with a fresh one since I have everything apart. I just need to know the specs on the thing so I order the correct one. Thanks
1/4" pipe is usually about 1/2" OD... If I remember correctly, 3/8" pipe is a bit over 5/8". Best thing, though, is probably just to measure it. Since it sounds like you've had it in your hands already (the debris comment), just take it to HD and match up the pipe thread part in their plumbing department. That way you know for sure what is on YOUR boat, not someone else's where it may be different.
If you have an outboard engine, you do not need that in the system. Just remove it and connect the barb fitting directly to the elbow.
It turns out that this valve is 3/8" barb and 3/8 NPT. Ordered a replacement a few minutes ago. Thanks for the replies and advice. JS
The idea of the AS device is to prevent draining (obviously). So actually, regardless of OB/inboard, if the fuel line drops below the top of the tank at any spot, then it's needed. This is just my opinion, of course, but I still like the idea since if a hose would rupture, the end may fall below the tank and start to siphon the fuel out... and the bilge pump will kick on and pump it overboard. The bilge "shouldn't" make a spark... but.... 
There are also huge EPA fines. It's a long shot that a hose would completely rupture, but better safe than sorry! Again, just my opinion on that part.
There are also huge EPA fines. It's a long shot that a hose would completely rupture, but better safe than sorry! Again, just my opinion on that part.Yes and no. In reality, all that matters is the level of the fuel. But because the level COULD be at the top of the tank, that's why the regulation is "higher than the top of the tank".
Although I now have the answer to my orig question, 3/8 barb with a 3/8 NPT thread, the discussion that has ensued is interesting, so I'll add my observations. At least on my 2003 228 Seafarer, the AS valve is screwed into the 90 deg fitting over the fuel pickup. The fuel line runs from the AS valve horizontally aft thru a bulkhead and then runs to starboard in the area that holds the live well, up to the water separator filter, and then on to the engine. The entire fuel line run is above the tank and thus above the fuel level. The valve opens for gasoline flow (obviously) and closes against and back flow. Any break in a fuel line inside the hull would drain fuel into the boat somewhere, Some fuel might even flow out of the tank depending on how full and the pitch of the boat.
It's my opinion that the anti siphon valve's intent is to keep fuel from draining backwards, away from the engine for whatever reason, hopefully preventing fuel pump cavitation etc. I don't see how it could do anything else. It should keep fuel in the line between the water separator and the tank, making recharging the fuel line easier.
Interested in any other views.
Vr/
It's my opinion that the anti siphon valve's intent is to keep fuel from draining backwards, away from the engine for whatever reason, hopefully preventing fuel pump cavitation etc. I don't see how it could do anything else. It should keep fuel in the line between the water separator and the tank, making recharging the fuel line easier.
Interested in any other views.
Vr/
Yup, good things to think about/discuss.
The amount of pressure needed (well, vacuum, actually) to open the AS valve (compress the spring) is greater than what a siphon can create. Meaning, a break in the fuel line will not create enough vacuum to open the AS valve. The intent of the AS valve is just that - anti-siphon (away from the tank).
The amount of pressure needed (well, vacuum, actually) to open the AS valve (compress the spring) is greater than what a siphon can create. Meaning, a break in the fuel line will not create enough vacuum to open the AS valve. The intent of the AS valve is just that - anti-siphon (away from the tank).
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jbs is correct though that the fuel in the line above the leak (toward the motor) may still drain out. It does however prevent the entire tank from draining.
I am down with the intent of the anti-siphon valve but I have seen 4 cases where that part caused engine problems. One of them was a brand new Edgewater 31.
One of them was my '84 V20. I replaced the tank and installed an anti-siphon valve to be "correct". Had to remove it that season. It got a straight thru hose barb. I added a manual shut off valve at the tank
Honestly I don't know if my Grady still has them. The tanks were changed by the PO and I have not messed with it.
I am down with the intent of the anti-siphon valve but I have seen 4 cases where that part caused engine problems. One of them was a brand new Edgewater 31.
One of them was my '84 V20. I replaced the tank and installed an anti-siphon valve to be "correct". Had to remove it that season. It got a straight thru hose barb. I added a manual shut off valve at the tank
Honestly I don't know if my Grady still has them. The tanks were changed by the PO and I have not messed with it.