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Old 18-02-2016, 15:09   #1
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Jabsco Quiet flush back siphoning

Hello everyone,

I thought I could work this out myself, but now I need some help.

One of our electric toilet keeps back filling with grey water even after changing out the macerator housing, the joker valve and the sanitation hose from the head to the holding tank. I have shortened the hose as it was quite long and had a big loop in it that took it below the level of the head. Despite this it still fills up with stinky water. Someone told me to put in a vent valve, but the other heads don't have them and they work fine.

Can any supply with the secret? Does the holding tank also have a joker valve where the hose from the head connects to it at the bottom of the tank? Thanks in advance.
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Old 18-02-2016, 17:47   #2
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Re: Jabsco Quiet flush back siphoning

Has it ocurred to anyone to check the holding tan vent for a blockage? That would pressurize the whole system, creating back pressure just like you describe.

Then I just saw this: Does the holding tank also have a joker valve where the hose from the head connects to it at the bottom of the tank?

Honey, the hose from the toilet connects to the tank at the TOP! The only line that should connect to the tank at the bottom is the pumpout line.

And btw...toilet waste is BLACK water... GRAY water is galley, bath or shower water.

It appears you need more one-on-one help to sort out how your system is supposed work than is practical in a discussion forum...in which case I'll be glad to help you if you'd like to send me an EMAIL (not a PM please?) I don't charge anything to help, btw..
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Old 19-02-2016, 08:02   #3
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Re: Jabsco Quiet flush back siphoning

Thanks Peg for your reply. I have opened up the pump out discharge vent to relieve any pressure in the tank, but no help.
Thanks for the clarification between gray and black water.
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Old 19-02-2016, 08:07   #4
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Re: Jabsco Quiet flush back siphoning

Sorry Peg, I hit the send button too soon.

The hose from our toilet does not go to the top of the tank. They go to the bottom of the tank, hence my question regarding a second joker valve at that point. We have three other heads that do not experience the same problem which is why I am slightly baffled at this point. Next step is to check the new joker valve and make sure it is not faulty.

Thanks again for our help. If you think of anything else please let me know.

Regards,

Karl
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Old 19-02-2016, 08:47   #5
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Re: Jabsco Quiet flush back siphoning

The hose from our toilet does not go to the top of the tank. They go to the bottom of the tank...

That has to be what's causing your problem...waste MUST enter the tank at the top, be discharged from a fitting at or on the bottom. Some tanks may have a discharge fitting on the top of the tank, but it will always have a pickup tube inside the tank to the bottom. To answer your question, A joker valve in the tank connection is NOT the answer...water and waste weigh 8.33 lbs/gallon. To use just 40 gallons as an example (with four toilets, I suspect yours is much larger), there'd be 333 lbs of pressure trying to turn a joker valve inside out...and it will succeed! I'll leave the rest to your imagination.
The ONLY solution to your problem: re-plumb the toilet discharge to enter the tank at the top. If the other toilets on your boat are also connected to the tank at the bottom, they're a disaster waiting for just the right moment...in which case the whole system needs to be replumbed.

Re-plumbing one toilet to a tank is a relatively simple job that any competent boat yard will know how to do correctly....however, 4 toilets connected to one tank on a 46' boat can be a real challenge that whoever created this mess obviously wasn't up to. There's a company called "Marine Sanitation" in Seattle that will know how to do it right. I strongly urge you give them a call. 206-633-1110 They service the whole PNW, and can come to you if you don't want to bring the boat down to Seattle.
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Old 19-02-2016, 09:00   #6
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Re: Jabsco Quiet flush back siphoning

Quote:
Originally Posted by Capt. Aubrey View Post
They go to the bottom of the tank, hence my question regarding a second joker valve at that point. We have three other heads that do not experience the same problem
Do the other heads also enter the holding tank at the bottom??

This sounds a very odd set up as you are going to be always fighting gravity.

The black water should enter the tank at the top.

Apart from anything else, by entering at the bottom you are asking for trouble with blockages as all the paper will settle at the bottom in the inlet pipe and not exit via the outlet pipe.

Anyway.

We have a joker valve on the loo base and the second non-return in the pipe about 1 ft beyond the joker valve. This certainly helps.

Making sure the pipe run is as short as possible helps and that it does not does not drop below the level of the WC will also help.

Keeping the pipes clear is also important.

Pore a bottle of Coke down it once a week and leave it to sit in the pipe over night will help
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Old 19-02-2016, 11:02   #7
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Re: Jabsco Quiet flush back siphoning

Hi,
I have had the same issue although my waste pipe goes through a diverter valve which either goes direct to the outside or to the holding tank. The pipe to the diverter valve has a high syphon bend in it. We did not get the problem when we had the old manual Jabsco. So for me it seems to be one of two things; either the toilet pump is not strong enough to pump all the waste water up and over the syphon or the pipe is constricted with lime scale and inhibits the performance of the pump. What is also obvious is that because there is water in the pipe, scale quickly forms on the joker valve; all it takes is a little bit to keep the valve open, and then you get foul smelling water coming into the bowl. What I will now say is that my old electric loo was replaced by Jabsco at no cost to me, other than fitting it. The old toilet was "jetting" a spout of water out of the bowl when trying to flush, plus it was backfilling. I sent Jabsco proof of purchase and that was it; a new quieter toilet arrived a couple of weeks later., and it seems to have a more powerful pump which so far seems to have done the job. I wait with baited breath to see if it will last. However, everyone I speak to recommends fitting a vent tube, unfortunately the syphon run lies behind a panel that is sealed in, and the pipes are cable tied down. Big job ahead to fit a vent tube and I want to change the pipes as well. Of course you need to have access to the vent tube so you can clean the valve every so often.
Good luck with yours, and I sincerely hope it does not turn into major headache.
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Old 19-02-2016, 14:06   #8
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Re: Jabsco Quiet flush back siphoning

... However, everyone I speak to recommends fitting a vent tube...

If you mean, put a vent line on the nipple of the vented loop instead of installing the air valve (aka "vacuum breaker") that belongs there, everyone you speak to is giving you bad advice.

That tube would so small--only .25 inch diameter--that the connection would quickly become clogged with salt and sea water minerals that you're already seeing on the joker valve and in the toilet discharge line...turning your vented loop into an UNvented loop that no longer has any ability to break a siphon.

Do a google search for "vented loop with vacuum breaker" to see the styles, mfrs and where to buy. It is NOT necessary to replace the vented loop, you only need to add the valve. And I'd get one for a spare because they do wear out...faster if they aren't cleaned as needed.
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Old 20-02-2016, 08:10   #9
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Re: Jabsco Quiet flush back siphoning

Thanks Peghall,
Totally agree. The vented loop with vacuum break is what I meant.

Cheers,

sjfk
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