Anti siphon valve question

[tomc585]

Ugggg...Just when you think you found the correct answer. There's always another "sub section".

 

[Bodick93]

ABYC standards require the anti-siphon remain in place In permanently installed fuel systems regardless of inboard or outboard applications.

2414.9.2 Installing an anti-siphon device at the tank withdrawal fitting or along the line, with a rated siphon protection head and flow rate greater than required for the installation.

24.14.11 Fuel distribution and retum lines provided with anti-siphon protection shall be installed in outboard powered boats equipped with permanent tanks, which shall terminate at a fitting at the stem where spillage will not enter the boat.

https://law.resource.org/pub/us/cfr/ibr/001/abyc.H-24.1993.pdf

Thank you. Great information.

 

[Jday]

I bought a new aluminum anti siphon valve and a brass straight thru one to replace the old one. I keep the boat about 100 miles away right now and just went to it this past week.

The old ASV came out without trouble, however, the new aluminum and brass ones would not thread on. It appears the old valve is a straight thread and the threads "NPT" on the new ones are pitched.

The new ones wouldn't even go on a full thread before they would tighten up, the old one would go on two or three threads before tightening up.

I punched out the ball and spring of the old one and reinstalled it for now. The tank is from 2004, were different threads used then? I'd like to have an ASV for safety.

I didn't want to force one of the new ones one for fear of stripping out the old threads on the tank. Has anyone ever had this problem.

 

[Bodick93]

No biggie, just carry them to HD or Lowes the next time you go, ID the threads, then order one online. I hate doing this, but another option may be to replace the whole assembly. I don't like doing this as there is always a chance of screwing up the tank threads if they are corroded, but it is an option. You have a short term solution. Don't rush the long term solution, and you will get it right.

 

[Puck-n-Fish]

It appears the old valve is a straight thread

What does the sealing for the straight threads? NPT threads are designed to seal but straight threads usually have an additional means of sealing (o-ring, flare, washer, etc.)

 

[tomc585]

I doubt its not NPT threads

 

[chas650r]

I doubt its not NPT threads

agreed, unless there is a o-ring of some type it's pipe thread. That being said I have had miss matched npt fittings more than once . if there is any leftover pipe dope in the threads a pipe tap for the female or a wire wheel for the male can also be necessary . I have had to tap the female deeper to get the less than stellar fittings to mate. look at the male parts closely , just a small ding in the first threads can be a no go.

 

[Jday]

Yes, it doesn't make sense to me the only valves I find are NPT and I would have a straight thread. This winter I plan on removing the pickup and running a tap through it. I'd do it on the tank, but I'm afraid I may get some debris down the pickup into the tank.

 

[tomc585]

You may end up with what I had...see post #3
Someone must have just run that fitting in and got lucky.
Maybe its best to pull the pickup tube out and go from there. It should come right out.