Vetus siphon breakers

Discussion in 'Diesel Engines' started by Jacques B., Mar 1, 2014.

  1. Jacques B.
    Joined: Oct 2013
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    Jacques B. Junior Member

    I'm contemplating the addition of a Vetus Airvent siphon breaker to my wet exhaust, but I don't quite get the concept.

    One apparently opens to the atmosphere and requires periodic maintenance, while the other "maintenance-free" version uses a thru-hull piss tube.

    Since I've got a 1/2" of steel hull to go through, I'd just as soon use the first option, but does that mean I'm going to get a constant dribble of raw water coming out of it?

    Thanks, as always, for your support.

    Jacques
     
  2. gonzo
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    gonzo Senior Member

    I have found that vents on the side of the hull can let water in in heavy weather. From personal experience, they can cause more problems than what they are supposed to solve. If you want a really simple anti-siphon, a vertical pipe or hose is all you need. The column of water needs to be enough to counteract the exhaust water pressure, which is very minimal.
     
  3. Jacques B.
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    Jacques B. Junior Member

    Thanks Gonzo,

    If I understood you correctly, all I need is a "T" fitting between the water manifold outlet and the exhaust elbow, with a single stack (tube) running vertically up from it.

    If so, what's the purpose of the Vetus Airvent loop w/valve?

    Don't get me wrong, I like your idea a whole lot better, but I'm new to wet exhausts, and I'm having a hard time grasping the "siphoning on shut-down" concept.
     
  4. gonzo
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    gonzo Senior Member

    The valve works where there is not enough headroom. However, like any other moving part, it can get stuck.
     
  5. Jacques B.
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    Jacques B. Junior Member

    OK, call me thick-skulled (you wouldn't be the first), but are you saying that all I need is a single, open-ended tube coming off of the water feed between the header and the exhaust elbow and sticking up a couple of feet above the waterline, or do I still need a "loop"?
     
  6. gonzo
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    gonzo Senior Member

    You don't need a loop, just a pipe open at the end. You can make it vent to the cockpit or deck just in case it occasionally overflows.
     
  7. Jacques B.
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    Jacques B. Junior Member

    Thanks gonzo!
     
  8. Jacques B.
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    Jacques B. Junior Member

    It's been a while, so I'll bring you up to snuff:

    Being just a few days away from re-installing the wet exhaust on my 90 HP Ford Lehman diesel, I revisited the engine room to map it out.

    Although she had no problem making the 300-mile ICW run from Fort Lauderale to Saint Augustine with the Vetus water muffler laying on its side at the bottom of the bilge and no riser to speak of on her 12 feet of 3-1/2" exhaust hose, I later learned of the need for a siphon break.

    Since then, Gonzo told me what I needed to do to create a siphon break, but now, I'm wondering where to put it.

    As you'll see in the pics below, there's a cylinder with a label on it between the heat exchanger and the water injection manifold that's also connected to the Velvet Drive using smaller lines.

    If at all possible, I'd like to know whether I should install the "T and siphon break stack" on the upstream or downstream hose of the cylinder, and while were at it, what that cylinder actually does.

    Thanks as always for your support.

    Jacques
     
  9. Jacques B.
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    Jacques B. Junior Member

    Whoops...
     

    Attached Files:

  10. michael pierzga
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    michael pierzga Senior Member

    The store bought siphon breaks are all funky.

    A weep hole thru the topsides is a stain, corroision problem.

    Many boats break the water column inside the boat.

    The classic example is dumping the siphon break line into the cockpit drain plumbing.

    The rules are that to choosen dump point should be near centreline and the that the dump pipe shall be routed high...on the engine room ceiling before discharging.
    In the picture the PP pipe entering the cockpit drain at the 90 elbow is the main engine siphon break. The other PP pipe is a bleeder to vent air from the seachest.
    [​IMG]
    subefotos
     
  11. gonzo
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    gonzo Senior Member

    Nice installation. You don't need more than a tiny hole to break the siphon action.
     

  12. michael pierzga
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    michael pierzga Senior Member

    A big hole is better. Hot seawater tends to foul a small hole very fast. Once that hole is plugged your system is useless. Think of how fast the pee hole on an outboard fouls.

    One advantage to breaking the syphon in a cockpit drain is that you can hear the Tinkle of water. No tinkle and your pump or sea chest has a fault.

    With cockpit syphon breaks be aware that when the ships exhuast outlet is underwater ...heavy weather or on a tack motorsailing....you can get back pressure exhaust fumes in the cockpit . If it was an enclosed cockpit you might wake up in the morning dead.

    My cockpit drain will turn black with exhaust when motoring in a gale.

    Be careful.
     
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