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Old 20-01-2012, 16:24   #16
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I think there are 2 in the suction and 2 in the discharge.
I'm sure I read a posting from Peggy Hall recomending all 4 be changed.
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Old 20-01-2012, 20:51   #17
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Re: Using a plunger on Vacuflush

John, I know what a duckbill valve looks like. I just was wondering, how or why corn kernels would jam it open. As opposed to anything else, i.e. a wad of tissue or excrement. I'm thinking...the relative density of corn, the small size not presenting enough area for the suction to grasp it and pull it clear?

It just seems, well, like another odd corollary of the law of unintended consequences or something. Somewhere some sanitary engineer is saying "Corn? Kernel corn? No, why on earth would we test it with canned veggies?"

I suppose it must be something like when Grace Hopper took apart the computer and found the world's first "bug" in the works...
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Old 20-01-2012, 21:13   #18
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Re: Using a plunger on Vacuflush

Why that should jam anything in the head, I don't understand. There would have to be some "gunk" for them to get stuck in. Perhaps decaying vegetable oil from someone who was using it to "lube" their head?

It's a buildup of solids and/or TP because you're not putting enough flush water through the system to keep it rinsed out. Get comfortable, class..."VacuFlush 101" is about to begin (and Btw...I had V/Flush toilets on my last two boats and was also a dealer for nearly 10 years...so I'm INTIMATELY acquainted with 'em...what keeps 'em working trouble-free and what doesn't.)

Part 1: How it Works

It's a 3 component system--the bowl assembly, the vacuum accumulator tank (not to be confused with a holding tank) and a vacuum pump. The vacuum tank and vacuum pump may be a combined gizmo called the "vacuum generator," but it includes both and works the same way as separate vacuum tank and pump. The holding tank is NOT part of the VacuFlush toilet system...SeaLand just bundles holding tanks with the toilet system.

The vacuum pump has TWO functions: it suctions the air out of the plumbing between the toilet bowl and itself while simultaneously pushing the flush the rest of the way to the tank, treatment device or thru-hull. The vacuum tank has a switch and a sensor on it that starts the vacuum pump when there's a loss of "vacuum" (toilet is flushed or an air leak in the system) and turns it off when the correct amount of negative pressure has been reached. How long it runs depends on the distance from the pump to the bowl...the shorter the distance, the shorter pump run time. The accumulated "vacuum" only pulls the bowl contents TO the pump..the pump has to push it the rest of the way.

Air leaks are the only thing that will cause the vacuum pump to cycle between flushes for no reason. The most common source of air leaks is worn out duckbill valves in the vacuum pump 4 of 'em--2 in, 2 out...so if it does start cycling for no reason, first thing to do is replace 'em. They should be replaced about every two years as preventive maintenance...even annually if you live aboard.

As duckbills become more worn, the pump will cycle more often and will run longer and longer each time. A failing vacuum tank switch can also cause the pump to run longer--till eventually it won't turn off at all unless you turn it off at the breaker--but that will NOT cause the pump to cycle for no reason.

Air leaks are the only thing that will cause the vacuum pump to cycle between flushes for no reason. The most common source of air leaks is worn out duckbill valves in the vacuum pump 4 of 'em--2 in, 2 out...so if it does start cycling for no reason, first thing to do is replace 'em. They should be replaced about every two years as preventive maintenance...even annually if you live aboard.

As duckbills become more worn, the pump will cycle more often and will run longer and longer each time. A failing vacuum tank switch can also cause the pump to run longer--till eventually it won't turn off at all unless you turn it off at the breaker--but that will NOT cause the pump to cycle for no reason.

Part 2: VacuFlush actual flush water Requirements (or, "What SeaLand doesn't want you to know")

The most common error that almost all VacuFlush owners make is believing SeaLand's claim that the V/Flush can use "as little as" 1 pint of flush water. That'll work in an RV gravity toilet because only enough water is needed to rinse the bowl after the bowl contents slides through the hole...but a VacuFlush system can be 15' long from bowl to vacuum pump and the suction splatters waste all over the inside of the hoses, vacuum tank and pump. If only urine is flushed...no water added to the bowl first, no TP either...then yes, you CAN get away with that little, at least for a few flushes. But if you do much of that, unless you want odor, at least once a day you need to run at least half a bowl of clean water through it to rinse out the system. It's also advisable to add at least half a bowl of water ahead of solids or any TP (iow, every time a female uses the toilet)...that's a quart or more. It's also essential to leave the pedal down for at least 7-10 seconds after the bowl is empty to rinse out the pump and duckbills--to prevent a buildup in the pump or bits of waste (maybe corn or peanuts???) or TP from becoming stuck in a duckbill, creating one of those pesky air leaks that causes the pump to cycle for no reason or keep running continuously. And if you don't want permeated hoses, it's a very good idea--last thing before the boat will sit (or at least once a week if you're living aboard)--to fill the bowl to the rim with clean water and flush it through to thoroughly rinse out the vacuum tank, hoses and pump...'cuz suction splatters waste all over 'em and the flush water flow isn't sufficient to completely fill the hoses. So, averaged out over a week, the VacuFlush actually NEEDS about the same amount of flush water as most other toilets that use pressurized flush water: about .5 gal. If you're using much less than that, you're asking for problems.
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Old 20-01-2012, 21:20   #19
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Re: Using a plunger on Vacuflush

There are 4 duckbills--two in, two out--and yes, they should all be replaced at the same time any are replaced...unless you just like pulling the hoses off each end of the pump and mopping up the spills about 4x a year instead of once every two years or so.

The SeaLand overboard discharge pump has two--one in, one out. I'd replace the duckbills in it at the same time the duckbills or joker valve in any toilet are replaced.
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