Exhaust anti siphon

[jackytdunaway]

The anti siphon valve has gone bad on my exhast water line and is letting water in. i have searched everywhere and can't seem to find anything. any ideas out in Sailnet land?

[ollie820]

Search under "vented loop" at West or Defender.

[jackytdunaway]

Mine has a brass fitting that has the diaphram in it and i was trying not to have to redo the whole loop just to replace the fitting or the diaphram.

[Valiente]

Good grief, I have been plagued by this on two boats now. The physics of putting a water-cooled engine at or below the waterline are dodgy to say the least. An option to make the vented loop "bulletproof" is not to rely on a spring-loaded plunger at the top of the loop, but to directly attach a length of hose from that barb directly up, if possible. Gooseneck the thing on deck if you wish. In other words, no "valve", no problem. No moving parts.

Same with the fuel and the water vent lines. Putting them at the waterline without valves is asking for trouble, just as putting an exhaust hose without the biggest riser you can rig (or even a waterlock aft) is trouble as well. I've always liked the idea of guys who've made a a "vent manifold" and run the lines up a stanchion or up a mizzen mast. Air gets in and does its pressure thing, but water can't.

Calder's books do a good job of explaining this, and will help you keep the sea out of your water and fuel tanks as the principles involved become clear.

[sailingdog]

I'd second the vent manifolds in the stanchions, since that is pretty fool proof...until you have to replace the stanchions. Vented loops can be problematic... and reducing the number of moving parts and complexity of a system is generally a good thing IMHO.

[Valiente]

Well, my vent hoses will all go up a four inch brass rail to the top of the pilothouse, near the centerline. I am sick to death of these type of issues, and all the older cruising books I have recommend goosenecks on the cabin sides, piping up the mast, basically anything but valves and topside vents. If you've got to have a hole on a boat, make it a loop pointing up.

[sailingdog]

If you're using a standpipe for the vents, you better make sure the end of it is pointing down, so that it doesn't fill up with water... It should look like an inverted p-trap from under your sink.

[jackytdunaway]

My problem with just letting it flow is that the hoses are on the cockpit side of my lazzerette and i would have to run quite a bit of hose and then T into something for it to drain anywhere but the bilge and i don't want it draining into the bilge. i have looked at the Vetus shown above and may go to that as a last resort. i amy just try to cut a new diphram out of rubber and see if it works 1st.

[Valiente]

Originally Posted by sailingdog

If you're using a standpipe for the vents, you better make sure the end of it is pointing down, so that it doesn't fill up with water... It should look like an inverted p-trap from under your sink.

Yes, that's what I meant by a "loop": a gooseneck, or ending in an inverted J with a bug screen on the end of it. Considering that most tank vents will make do with a fairly small ID hose (just to equalize the air pressure), it's not a tough fix when combined with a brass pole that makes a good handhold in the pilothouse. I'll have to go to a strip club yard sale, I guess.

I have some design books from the '70s, back when boats were considerably more "shippy" than today, and I've revived some very useful design ideas from them. Getting the vents high and dry is only one.

[Valiente]

Originally Posted by RickBowman

The engine vented loop in my PS is routed aft through the engiine room through the bottom of an interior stowage compartment then up into the port cockpit Lazarette, well hidden and inaccessible behind the water heater which puts it about 3" below the bottom of the stanchions. This image was captured without being able to look through the viewfinder of the camera. Yes, I am rather screwed if this vent needs maintenance. The water heater would have to be removed for access to the vent.

To make that bulletproof, run a small line from the top hole on the cap to the outside. That's a Vetus or a Vetus knock-off. They are probably the best, if at least 16" above the waterline.