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Old 05-28-2018, 06:18 PM   #1
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Jabsco head

Manual jabsco. I pump out the liquids and 5 mins later the bowl is full again. I run the macerator and the bowl empties only to fill up in about 10 mins. I empty the macerator and the bowl fills up again. Is this calling for a new pump or the famous "Joker/duck valve replacement. Any advise appreciated, as always. Thanks
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Old 05-28-2018, 06:34 PM   #2
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I have electric heads and one was doing that. It was the joker valve.
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Old 05-28-2018, 07:54 PM   #3
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The joker valve is only a band aid that'll keep back flow from flooding the bowl...it won't prevent the backflow...and it'll only work as a band aid until it becomes worn enough to let the backflow get past it.

Questions first: "I run the macerator and the bowl empties only to fill up in about 10 mins"

You said you have a manual toilet...There is no macerator in any manual toilet. So WHAT macerator??? The only macerator pump in your system should be the one to dump the tank. And that one shouldn't be run when flushing the toilet. (Please don't tell me you've installed a macerator pump to replace the manual toilet pump???)

What's filling up into the bowl--a flush backing up, or clean flush water?

Has the toilet gradually gotten harder to pump?

When I know the answers I think I'll know what the problem is.

Peggie
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Old 05-28-2018, 08:22 PM   #4
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the backflow is not from the fresh water flush, its coming back from the holding tank so it probably is the joker valve ???
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Old 05-28-2018, 09:14 PM   #5
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Quote:
Originally Posted by Joew2604 View Post
the backflow is not from the fresh water flush, its coming back from the holding tank so it probably is the joker valve ???


My understanding is that the joker valve is NOT meant to stop backflow from the holding tank to the toilet. It sounds as if your system has a big problem. If your holding tank is getting pressurized, then that pressure will overcome the resistance of the joker valve.

When was the last time your holding tank was emptied? Are you sure it really is empty?

Is your vent working properly? When you flush the head, your vent should expel and equal amount of air as the volume of waste flushed.
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Old 05-28-2018, 10:06 PM   #6
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The joker valve can block back flow, but it can't CREATE back flow. Something is pushng flushes back to the toilet. A brand new joker valve can slow it down to slow seepage....if it's coming into the bowl as a flood, the joker valve is WAAAAY overdue for replacement, but replacing it won't solve the problem.

You only answered one the questions I asked you. I didn't ask the others solely out of curiosity, I need as much info as possible to diagnose your problem. So I'd appreciate the answers to the rest of 'em.

However, based on what little info you've provided, I have a strong suspicion that the culprit is a blocked holding tank vent. When air displaced by incoming flushes has nowhere to escape, the tank--the whole system--becomes pressurized, preventing flushes from even getting TO the tank. And btw, unless your holding tank is full to overflowing, it's highly unlikely that it's actually holding tank contents that are backing up, 'cuz the inlet from the toilet is at the top of the tank and contents below that fitting don't jump into it. So what you're seeing is waste in the toilet discharge line that isn't making it to the tank.

So before using the toilet again or especially before trying to pump out or dump the tank, make sure the tank vent is clear, 'cuz continuing to flush against a blocked tank vent will continue to pressurize the system...a pumpout or overboard discharge pump will pull a vacuum that won't let it pull out more than a gallon or two.

Blockages rarely occur in the vent LINE. The vent thru-hull and the other end of the vent line--the vent fitting on the tank and that end of the hose--are almost always where blockages happen.

Start with the vent thru-hull: use a screwdriver blade or whatever works to scrape it out. If there's a screen in it, knock it out...screens cause more problems than they solve. Next, open the deck pumpout fitting...VERY CAREFULLY, with a hose at the ready, 'cuz a pressurized tank can spew a geyser. Then remove the vent line from the tank and scrape out both the tank vent fitting. Now flush the toilet to see whether there's still back pressure in the system. If not, you've solved the problem. If there is, there may be a clog in the toilet discharge line.

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Old 05-31-2018, 08:40 PM   #7
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The bowl on my Jabsco head kept filling up. After checking everything I found that the holding tank kept filling upafter about an hour. The water is coming from the macerator which is connected to the underwater thru hull. The path is from the thru hull, through the macerator and into the holding tank. I tuenrd off the valve on the thru hull and now the holding tank doesnt fill up and neither does the bowl. Question is -- Should the thru hull valve be closed, except when pumping out the holding tank. Appreciate some of your knowledge. Thanks
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Old 05-31-2018, 10:12 PM   #8
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Question is -- Should the thru hull valve be closed, except when pumping out the holding tank. Appreciate some of your knowledge. Thanks

Yes! And because people aren't infallible and can forget to close it, there should also be a vented loop that's at least 6-8" above waterline in the line between the macerator and the thru-hull. If that's impractical, move the macerator pump to a location above the tank--or at least at the same level as the top of the tank. Neither loop nor the elevated macerator pump will prevent water being forced up the thru-hull while the boat is underway, it will save your boat if you forget to make sure it's closed before leaving the boat because water will only rise that line to the boat's waterline. However, that's NOT a reason to leave that thru-hull open except in actually in use.

Also make sure your toilet intake thru-hull is closed when you leave the boat. And if there isn't a vented loop in that line, install one. You'll find an illustration showing the correct location for it in the owners manual for your toilet.

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