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Old 03-03-2020, 07:57 PM   #1
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Full flow check valve in sanitation line

I am rebuilding my waste / sanitation plumbing system and all of the check valves that I see at WM / Defender are not full flow "flapper type".
The moving parts restrict the cross sectional area and I am concerned about efficiency. Am I over thinking this from an Engineers perspective ?
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Old 03-03-2020, 08:05 PM   #2
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Tom, are you referring to 'joker' or 'duckbill' valves?
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Old 03-03-2020, 08:22 PM   #3
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Where are you planning to use check valves in the sanitation system?
Usually the only check valves are the Joker at the toilet output itself and the Duckbills on the waste tank pumps such as the Sealand, now Dometic units.
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Old 03-03-2020, 08:30 PM   #4
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Not the duckbill type. The inline type that has a piece of rubber across the opening. Only the rubber does not open all of the way to agree with the Ř 1.500 opening of the hose.
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Old 03-03-2020, 08:36 PM   #5
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Maybe Peggie Hall will chime in. I've never heard of what you describe. I'm interested since I just re-did my system a few months ago. New Raritan SeaEra heads and new 1.5" discharge hose to the holding tank.
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Old 03-03-2020, 09:06 PM   #6
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I am not the expert that Peggie by far, but I have not seen check valves in waste systems. Except the aforementioned duck bill valves. Check valves sound like a place for clogs to start.
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Old 03-03-2020, 09:14 PM   #7
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I agree about the clogs, that is why I wanted a full flow check valve. our 30 yr old system has ultimate flexibility with all options of waste management and legal disposal.
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Old 03-03-2020, 09:29 PM   #8
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I'm happy to chime in here, but I've read the whole thread this far and I have no idea what he wants to accomplish, but what he's written so far suggests that he may be trying to over-engineer something that's actually pretty simple. He's welcome to contact me directly if it's in more detail than is practical in a forum post.

However, 30 years exceeds the lifespan of even the best marine toilets without the need for repairs that can cost more than they're worth. So it might be time to consider replacing everything.

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Old 03-03-2020, 11:08 PM   #9
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No idea where you’d need a check valve in a sanitation system but why not just go a size larger on the check valve? Put a 2” check valve in a 1-1/2” line.
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Old 03-04-2020, 10:33 AM   #10
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I am replacing hoses and fittings as I put it back together with new items. Maybe that is the problem, some hoses are still disconnected ?
I also noticed that there is no anti syphon loop on the macerator discharge line.
What is happening is my waste tank is filling up with seawater, I will investigate more today. All comments are welcome,
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Old 03-04-2020, 10:55 AM   #11
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Quote:
Originally Posted by TJM View Post
I am replacing hoses and fittings as I put it back together with new items. Maybe that is the problem, some hoses are still disconnected ?
I also noticed that there is no anti syphon loop on the macerator discharge line.
What is happening is my waste tank is filling up with seawater, I will investigate more today. All comments are welcome,
An anti-syphon loop would be a better solution than a check valve.
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Old 03-04-2020, 01:39 PM   #12
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Parks is right...there should be a vented loop in the tank overboard discharge line, not a check valve. The vented loop should be installed between the overboard discharge pump (electric or manual) and the thru-hull. However, even without a vented loop the tank cannot take on sea water if the thru-hull is kept closed--as it should be, with or without a vented loop in the line, except when actually dumping the tank.


A check valve is actually a bad idea because a) waste is not only sticky, but the animal fats in it can build up and clog the valve, same as it does senders on tank level monitors that are inside the tank...and b) just looking at a joker valve in a toilet discharge fitting that's been there more than a year should make it obvious that check valves wear out fairly quickly, requiring replacement. So a check valve would just be swapping one problem for a new one.


You MIGHT be able to get away without the vented loop if you can mount the macerator pump above the tank. But that still wouldn't excuse the need to keep the thru-hull closed except when actually dumping the tank.



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Old 03-04-2020, 01:44 PM   #13
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Quote:
Originally Posted by TJM View Post
I am replacing hoses and fittings as I put it back together with new items. Maybe that is the problem, some hoses are still disconnected ?
I also noticed that there is no anti syphon loop on the macerator discharge line.
What is happening is my waste tank is filling up with seawater, I will investigate more today. All comments are welcome,
Is your head an electric one? I had one that the fill valve had a tiny piece of debris stuck in it. The head would slowly fill and then siphon into the holding tank. Replaced the fill valve and had no more issues.
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Old 03-05-2020, 07:10 AM   #14
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"An anti-syphon loop would be a better solution than a check valve"


Works best AND its KISS!
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Old 03-05-2020, 09:00 PM   #15
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Adding the Anti syphon vented loop solved the problems. The PO just had a loop in the engine room between the Macerator and the thru hull ball valve.
Peggy, thanks for the info about closing the ball valve unless in use in legal areas. I never thought about closing the valve. The Macerator breaker is “locked out” but closing the valve is a better level of protection. Thank you.
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