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Old 02-06-2012, 14:12   #31
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Re: Vent Loop on Head

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Originally Posted by HopCar View Post
Pete7, there is no point in having loops unless you put a vent at the high point. Without a vent a siphon can get started and overflow the toilet unless the rim of the bowl is above the waterline. If as you say the head is above the waterline, you won't have a problem.
I wonder if the loop is there to ensure if the yacht leans over there won't be a problem. However, we are religious about closing seacocks before we leave.

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Old 02-06-2012, 18:06   #32
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Re: Vent Loop on Head

With respect to vented loops and the waterline; the waterline in question is the heeled waterline.
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Old 02-06-2012, 20:22   #33
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Re: Vent Loop on Head

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If your toilets are above the waterline all the time, you don't need vented loops. If you never forget to close the seacocks you don't need a vented loop. If you ever take apart a toilet pump and look at the valves inside, you wouldn't trust them to keep your boat afloat.
Pete7, there is no point in having loops unless you put a vent at the high point. Without a vent a siphon can get started and overflow the toilet unless the rim of the bowl is above the waterline. If as you say the head is above the waterline, you won't have a problem.
Not totally true. Your heads and more particularly, critical plumbing geometry may drop to below waterline under sail & healed.
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Old 02-06-2012, 22:03   #34
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Re: Vent Loop on Head

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Good discussion...

Does anybody have a vented loop on the head intake side.?
I got one and seem to remember that it is not necesarry, but for some reason previous owner of factory installed it..

Just about to remove the loop but just want to make sure it is not required for insurance purpose or for not getting dinged when selling and surveying the boat..
My head had been fitted like that at some point prior to my buying the boat. The intake hose always had air in it, and sucked air when flushing. The seal on the pump that separated raw water inlet and maserated outlet did NOT like running dry and allowed the product of the maserator to mix with the flush water, not the most pleasant of reclycling practices.
Correct installation with a vented loop between pump outlet and bowl solved all problems.
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Old 02-06-2012, 23:17   #35
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Re: Vent Loop on Head

Wotname, thank you for making that clear. That was what I was alluding to when I said "If your toilets are above the waterline all the time...". Of course the waterline changes dramatically and for long periods of time when a boat heels. A toilet that is normally well above the waterline can end up below the waterline when the boat is heeled. In that case vented loops are a very good idea.
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Old 27-07-2013, 09:51   #36
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Re: obtaining duckbill part

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Otoh, a lot of people don't know that air valves need regular cleaning and occasional replacement either....
I just bought a boat that has a "vented loop" by Forespar, but it is missing the duckbill. I won't be graphic about what that is causing in the locker behind the potty, but you might be able to imagine.

Now, as for replacement... where can I get a few of those little duckbill thingies? I don't see them for sale on Forespar's site; they want to sell the whole $38 fixture, and I only want the 38 cent duckbill. Has anyone ever found a supplier?
sj
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Old 27-07-2013, 09:59   #37
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Re: Vent Loop on Head

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Maybe I read the OP wrong but my question would be. How can your head draw water in, which creates a vacuum, if you have a vented loop between the seacock and the pump. When I installed my raritan I installed the vent between the pump and bowl which works great. Am I missing something?
You theoretically need both, one on the outlet side and one on the inlet side.

Regarding the input (your question), the hole is quite small in most of those arrangements (to make the "vented" loop). So it's a relatively tiny amount of air. It does impede the suction of water, maybe by ~30%, depending on other variables.

There are other creative ways to solve the problem though. I run a small hose, fitting over the nipple of the vented loop, and near the flush button (electric head). When I want more water, I just put my finger over the hose. It stops the air, and all is good.

If I got really smart I could wire up some kind of solenoid that's open when the head is flushing.
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Old 27-07-2013, 10:45   #38
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Re: Vent Loop on Head

Rebel that is a great idea! the owner of the boat mentioned in post 23 has complained of it not flushing well since the install of the vent and I failed to mention another point leading to near sinking,a bilge pump with an OFF position switch,why would one want a bilge pump with an off position??
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Old 27-07-2013, 11:16   #39
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Re: Vent Loop on Head

On thing you can do to keep the valve clean; if you have room above the loop, put a piece of hose on the top of the loop and separate the valve above the loop by 6"-12". This helps to keep the crud out of the valve immensely. It's the valve that need to be up... so you can lower the loop if necessary.
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