anti-syphon repair

[xort]

I have an anti-syphon loop for my shower sump pump. It is brass of unknown origin, circa 1985. It has a screw-on cap with hole in it. The U shaped fitting looks to be 3/4". Local chandlery does not have parts. The old rubber thingy inside fell apart and needs replacement. I have several more of these on the boat. I'd like to find the rubber replacement part instead of replacing the whole loop. Local plumbing supply house said good luck. Defender doesn't have anything.
Where do I find this little rubber part for the anti-syphon loop???

[JohnRPollard]

XORT,

I think we'll need to see a photo or at least a manufacturer's part no. We did a thread a month or two ago on anti-siphon valves (for the engine raw water intake, I think, Denise might have started it). There were some photos posted there. Does it look anything like those?

[xort]

The brass cap with a hole in it screws onto the top of this. There is a rubber part that does the anti syphoning work inside the brass cap.
I can find no name

[WinterRiver]

I think this is the piece, called a vent cap:


Discount Marine and Boat Supplies - Inflatable Sales - Defender

I found one at WM when I lost the litte rubber part into an inaccessible area.

[xort]

That looks like it would work but no info on size. I called Defender yesterday and they didn't mention this. "Vent Cap" didn't enter into the conversation.

Meantime, I read elsewhere to put a bit of rubber gasket material inside the cap and poke a pinhole in it. It seems to work but not sure of it's anti-syphon capability.

[jackytdunaway]

That looks like it would let the water out and not the air in. i wonder if it can be reversed. If so i can use one that fits my anti-syphon. right now i have a gas anti-syphon turned backwards connected with a hose to the top of the loop. my old one failed and i could not find one