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Jabsco head seepage back into bowl from holding tank

Jul 30, 2019
208
Seaward 25 777 Fort St. James
Newly acquired 2000 vintage boat with original Jabsco head. Trailing her home, with the valve on "dry bowl" setting, I got seepage of unpleasant fluid back into the bowl. The holding tank only had a little in it. In the exploded diagram below, number 32 is described as a "joker valve", although I think that should be choker valve. Is this the culprit?


20200601_162430.jpg
 
May 17, 2004
3,427
Beneteau Oceanis 37 LE Havre de Grace
It really is called the joker valve, and yes those symptoms sounds exactly like that’s the problem.
 

Apex

.
Jun 19, 2013
1,034
C&C 30 Elk Rapids
get Peggie Hall's book. But right off, pressure in the holding tank is often the cause. make sure vent lines to the tank are clean and clear. Upsize to 1" if possible. THOUGH trailering speeds may be culprit for pressure (55mph). The joker valve is expendable (1-2yrs).

...search the forums, this is teh most common asked question, coming to pressure and worn components.
 
Dec 2, 1997
8,087
- - LIttle Rock
The backflow is NOT coming from the holding tank. The inlet fitting on a holding tank is at or on the top of the tank...you've said there's very little in the tank, which means tank contents would have to jump up to the inlet fitting to run back to toilet unless the tank is lying on it's side. So what IS running back is waste that never made it into the tank, is left sitting in the toilet discharge hose.

The wet/dry mode has nothing to do with OUTbound waste in the bowl...the WET mode, allows the pump to pull flush water IN, the DRY mode blocks incoming flush water.

A brand new joker valve (yes, that IS what it's called...I don't know why either) will prevent back flow, but only till enough flushes have gone through it to stretch the slit in it. At first it's slow seepage, but the more flushes that go through it, the wider the slit gets...until it finally becomes a hole. If it's never been replaced, it might as well not even be there.

If your toilet is original on a 10 year old boat, it's 10 years old...the average life of a Jabsco manual toilet pump is 2-5 years, so I suspect the pump has been replaced at least once. A replacement pump is inexpensive (forget installing a "service kit"...it's a PITA to do and the price is 85-90% of the price a new pump) and replacing it is easy--remove the 4 bolts that hold it on the base, remove the inlet and discharge hose...bolt the new pump the base, replace the hoses...and it's done. There will be a new joker valve in the new pump...it should be replaced annually--or at least every two years.

At the risk of being accused of a little shameless self-promotion, I'm gonna second Apex recommendation to buy my book (see link in my signature). The title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance on your terms when it's convenient...the need to cure a problem never happens when it is! And I'm always glad to answer any questions it doesn't.

--Peggie
 

TAK

.
Nov 29, 2009
47
Beneteau 381 Herrington Harbour South
Agree with the vent line and 1 to 2 seasons comment. New joker valve takes 5 minutes plus a bit more to clean up. Pump some fresh water through the toilet before starting.
 
Jul 30, 2019
208
Seaward 25 777 Fort St. James
Thank you Apex. The first owner changed the holding tank system ti a "KISS Type III MSD" system, as described here:


All lines, including vent, are about 1-1/2" ID to judge from their external appearance. The holding tank is high in the starboard lazarette, occupying otherwise underutilized space.

20200522_150718_resized.jpg
 
Jul 30, 2019
208
Seaward 25 777 Fort St. James
Thanks to everyone for the info. I think this one is solved. Joker valve will be replaced. Simple question, simple answer.
 
Jan 19, 2010
9,953
Hunter 26 Charleston
The backflow is NOT coming from the holding tank. The inlet fitting on a holding tank is at or on the top of the tank...you've said there's very little in the tank, which means tank contents would have to jump up to the inlet fitting to run back to toilet unless the tank is lying on it's side. So what IS running back is waste that never made it into the tank, is left sitting in the toilet discharge hose.

The wet/dry mode has nothing to do with OUTbound waste in the bowl...the WET mode, allows the pump to pull flush water IN, the DRY mode blocks incoming flush water.

A brand new joker valve (yes, that IS what it's called...I don't know why either) will prevent back flow, but only till enough flushes have gone through it to stretch the slit in it. At first it's slow seepage, but the more flushes that go through it, the wider the slit gets...until it finally becomes a hole. If it's never been replaced, it might as well not even be there.

If your toilet is original on a 10 year old boat, it's 10 years old...the average life of a Jabsco manual toilet pump is 2-5 years, so I suspect the pump has been replaced at least once. A replacement pump is inexpensive (forget installing a "service kit"...it's a PITA to do and the price is 85-90% of the price a new pump) and replacing it is easy--remove the 4 bolts that hold it on the base, remove the inlet and discharge hose...bolt the new pump the base, replace the hoses...and it's done. There will be a new joker valve in the new pump...it should be replaced annually--or at least every two years.

At the risk of being accused of a little shameless self-promotion, I'm gonna second Apex recommendation to buy my book (see link in my signature). The title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance on your terms when it's convenient...the need to cure a problem never happens when it is! And I'm always glad to answer any questions it doesn't.

--Peggie
:plus:
I have a copy
 
Jan 22, 2008
8,050
Beneteau 323 Annapolis MD
Agree with the vent line and 1 to 2 seasons comment. New joker valve takes 5 minutes plus a bit more to clean up. Pump some fresh water through the toilet before starting.
Item 15 might be suspect, though I've never had to deal with it myself. Raritan makes a good joker valve, a 253 and a 254. IIRC, the 253 fits in the Jabsco, so is what I replace J's with. You can see the difference in the 253/254, enough so you should be able to ID the right one. If I can find the right number, I'll come back and post it.
 
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jec1

.
Jul 27, 2021
2
Jeanneau 44 DS Seattle
We have a similar problem, just bought a 2016 Jeanneau with a Jabsco manual head. The bowl was filling up with waste water which I believe is from the hose that goes to the top of the tank. Yesterday I replaced the entire pump assembly with a new pump assembly, which included a new joker valve. It worked well yesterday, but this morning the bowl was full of waste water again. Am I overlooking something here? I thought the new joker valve and pump assembly would fix it.
 
Dec 2, 1997
8,087
- - LIttle Rock
If I read you correctly, it's an uphill run from the toilet discharge to the tank inlet. So if you aren't pumping enough times in the DRY mode to push the flush all the way into the tank, what's left in the line will do what water an just about everything else does: run downhill to the toilet. The joker valve only keeps it out of the bowl until it becomes too worn to do so.

Read post #10 in this thread for more info.

--Peggie
 

jec1

.
Jul 27, 2021
2
Jeanneau 44 DS Seattle
If I read you correctly, it's an uphill run from the toilet discharge to the tank inlet. So if you aren't pumping enough times in the DRY mode to push the flush all the way into the tank, what's left in the line will do what water an just about everything else does: run downhill to the toilet.
Yes, the discharge from the toilet goes vertically about four feet then into the top of the tank at a right angle fitting. Wouldn’t pumping in the dry mode just send air bubbles up through the waste in the 1-1/2” hose, especially if it is mostly liquid waste? Thanks!
 

Apex

.
Jun 19, 2013
1,034
C&C 30 Elk Rapids
I think that is the point, empty the hose as much as possible so the #'s are not sitting in the hoses, but in the tank. Anything left in the hose is being pushed by gravity back to the loo