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Old 22-10-2015, 09:21   #16
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Re: Anti Siphon on the waste output

maybe I'm confused, I understood most (all?) setups should have a vented loop on the intake (inlet) side?
many diagrams I've looked at show it, like the attached.

..edit
and just saw your reply Peggie, thanks for that, great details.
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Old 22-10-2015, 09:32   #17
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Re: Anti Siphon on the waste output

Drawing shows exactly where both intake and discharge vented loops belong. Notice that they show an air valve in the top of each one.
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Old 22-10-2015, 09:59   #18
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Question Re: Anti Siphon on the waste output

Quote:
Originally Posted by peghall View Post
I think he means the TOILET intake. If so, it doesn't belong in the intake line between the thru-hull and the pump..it has to go between the pump and the bowl because the pump PUSHES water to the bowl. And there needs to be an air valve in the loop to prevent squirting.

The loop in the tank discharge line should go in AFTER the pump. It too needs an air valve.

Too many people don't even know what an air valve is, or that vented loops are supposed to have one. So they think the solution to a loop in a discharge line that squirts is a vent line....not realizing that because that line is so small--typically only 1/4" ID--it quickly becomes clogged up with sea water minerals or waste...turning the loop into an UNvented loop that no longer has any ability to break a siphon. And because the vent line has solved the squirting problem, it's "out of sight, out mind"...never occurs to anyone to clean it. Air valves also should be removed and cleaned and replaced when worn out.
Peggie, perhaps I misread but it was proposed to put vented loop on intake side in order to break siphon affect? As I understand because loop is vented then vent would open on negative pressure (suction) when attempting to draw water in to the head. If vent is a manually released valve at end of pumping cycle it would work.
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Old 22-10-2015, 11:49   #19
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Re: Anti Siphon on the waste output

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Originally Posted by mtompson View Post
...I would only ever open the seacock when I was pumping out, this setup would rely on the one way valve inside the pump...


Pretty hard for me to believe what you guys have turned this simple system into.

The above diagram shows precisely the way it should be installed. There is no reason for pumping out the top of the tank. And no need for a vented loop, as the sea cock would only be open during pumpout at sea.
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Old 22-10-2015, 12:13   #20
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Re: Anti Siphon on the waste output

thanks Terra, I appreciate getting the safer methods as well, at least then I can make an educated decision, l have 3 kids to worry about, and while I could lock that seacock ( which I may do even with a loop ) I can have some peace of mind with the safer setup.
Nice you liked my first setup though
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Old 22-10-2015, 12:18   #21
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Re: Anti Siphon on the waste output

Adding unnecessary components and longer hoses will not make it any safer.
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Old 22-10-2015, 13:39   #22
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Re: Anti Siphon on the waste output

I agree, this is exactly why I think this forum is so good, I don't want to make any quick decisions, I really appreciate eveyones ideas & experience.
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Old 22-10-2015, 14:25   #23
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Re: Anti Siphon on the waste output

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Originally Posted by Terra Nova View Post
There is no reason for pumping out the top of the tank. And no need for a vented loop, as the sea cock would only be open during pumpout at sea.
There's a very good reason for putting the discharge fitting in the top of the tank, with a pickup tube inside to the bottom: When the discharge fitting is at the bottom of a tank, waste will rise in that hose to the level in the tank, keeping that hose full of waste to permeate. When the fitting is on the top, that line is inside the tank.

While there's no need for a vented loop between the toilet and the tank, safety standards call for one in any line that connects to a below-waterline thru-hull. The thru-hull SHOULD only be open during pumpout, but humans are faillible...the loop protects the boat from human error. You can never go wrong erring on the side of caution.
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Old 23-10-2015, 02:59   #24
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Re: Anti Siphon on the waste output

With a view to keeping hoses as empty as is possible, what would normally happen on the red side in this diagram.
Is it the case that once your pumping air out you can quickly shut the Thru hull before the sea moves up the hose?
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