Anti-siphon loop for engine

Click through the link

http://www.vetus.com/vetus-beluchter-met-klep-voor-13-19-25-32-mm-slang-4839.html
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sailorman said:
Engines_and_around_180px_hoog_2.jpg


http://www.vetus.com/engines-and-around-the-engine/cooling-water-system.html

http://www.vetus.com/videos/all/engines-and-around-the-engine.html 8 mins into the video
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Thanks, interesting video about installing the engine, but see pvb's post.
I wish my engine compartment was/will be as easy to work in and as spotless:eek:
Tranona said:
It fits anywhere downstream of the seawater pump, usually in the hose from the heat exchanger to the injection point in the exhaust (if there is one). Otherwise in the run from the seawater pump to the engine. Taken well above the waterline, its purpose is to vent the waterpipe when the engine stops to prevent syphoning back. Good explanation in the Vetus catalogue or on their website.
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Thank you. That clears up my mystification. I'm amazed my current engine doesn't have one; unless it's hidden amongst all the other "pipe-work" in the dark depths!

john williams said:
Good stuff everyone - thanks for your help

John
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+1
pvb said:
I'm sure you mean to be helpful, but the link you posted doesn't actually show anti anti-syphon products.
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Maybe not, but it shows a pipe and T-piece being fitted, which I assume is the anti-syphon arrangement

Thank you one and all
R
 
My boat came already fitted with a Vetus (I think) anti syphon device......would it be easy to retrofit one of the aforementioned "piddling tubes" which seem to be reccomended by everyone? (Nigel Calder, Hal Roth et al). I don't want to get into any welding as its way outside my skillset......
 
Tim O said:
My boat came already fitted with a Vetus (I think) anti syphon device......would it be easy to retrofit one of the aforementioned "piddling tubes" which seem to be reccomended by everyone? (Nigel Calder, Hal Roth et al). I don't want to get into any welding as its way outside my skillset......
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I think its just remove the valve thingy & add a pipe. i think they all come with the pipe spiggot
 
Tim O said:
My boat came already fitted with a Vetus (I think) anti syphon device......would it be easy to retrofit one of the aforementioned "piddling tubes" which seem to be reccomended by everyone? (Nigel Calder, Hal Roth et al). I don't want to get into any welding as its way outside my skillset......
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Then all you need is a reducing tee, as shown top left of the second pic post #11. Garden centre will most likely sell you one for peanuts. Also available in brass.
 
Paul.....where would this reducing tee go.....before, after, or instead of the Vetus part (which is between heat exchanger and exhaust injection point). Presume would run a small pipe from the Tee up to spill/pee into the cockpit?
 
Tim O said:
Paul.....where would this reducing tee go.....before, after, or instead of the Vetus part (which is between heat exchanger and exhaust injection point). Presume would run a small pipe from the Tee up to spill/pee into the cockpit?
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Instead of the Vetus part. Pee pipe to cockpit or over the side. Mine is connected to a small fitting just over the gunnel. It pees overboard, but you can still see it. Mine is fitted between the water pump and heat exchanger, same as Sailormans, up as high as it can go in the engine bay, but fit it where the engine manufacturers recommend. Obviously only want a small pee hole, or it'll pump too much water overboard
 
Tim O said:
Paul.....where would this reducing tee go.....before, after, or instead of the Vetus part (which is between heat exchanger and exhaust injection point). Presume would run a small pipe from the Tee up to spill/pee into the cockpit?
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Do you already have the Vetus vent ? If so, forget my suggestion, i was under the impression you didn't have one.
 
Yes, I have the Vetus vent (valved one I suspect)......but fancied the idea of the pee pipe giving a constant visual check that cooling water system is running.....especially as with my centre cockpit I can't see or hear the exhaust outlet at the transom without leaving the helm....
 
Tim O said:
Yes, I have the Vetus vent (valved one I suspect)......but fancied the idea of the pee pipe giving a constant visual check that cooling water system is running.....especially as with my centre cockpit I can't see or hear the exhaust outlet at the transom without leaving the helm....
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My mistake, didn't realise you had it. You may as well use what you have, but you can remove the valve and fit a pee pipe.
 
Try Aquafax, who have an anti siphon valve well below £10. Add a couple of off the shelf bronze threaded fittings & behold you have made your own A/S loop.

The valve in question has the distinct advantage that it employs a floating ball as the mechanism, whilst most others have a very tiny orifice & an equally tiny & flimsy membrane that needs regular maintenance.

This arrangement has protected my Beta 25 for over 1000 hours & has been absolutely problem free.
 
VicS said:
It needs to be a raised loop with the vent at the highest point, not just a T piece in the existing pipework with a raised vent hose.

No reason not to make up a suitable fitting and easy if you opt for the type that just "pees" overboard or into a cockpit drain.

With the peeing type you know if it's peeing that it is not blocked etc. The valved type need regular maintenance and often dribble into the bargain
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All Westerly yacht were fitted with this over the side pee job - dead simple and infallible, until one of those little Mediterranean wasps make it their home for the winter! Check why the water is not coming out - no water, no break in the siphon.
 
A lot of AWB's don't need them.
If the mixing elbow is above the waterline, it won't syphon anyway. Obviously a bit of margin for heeling etc is good.
 
VicS said:
Vetus recommend an anti-siphon loop if the injection point is less than 15cm above the W/L:

http://viewer.zmags.com/publication/39b85263#/39b85263/84
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Beta are slightly more cautious and go with 25cm in their 'Engine Installation Guide'. They also make the recommendation that, in a yacht, the anti-siphon valve should be as close to the centreline as possible so that there's no possibility of the valve dipping below the waterline when heeled.
 
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