Jabsco toilet bowl backfilling

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eddystone

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Recently the bowl on my Jabsco toilet has been filling to half/third height after flushing. Could this be scale build up or valve wear; there is no holding tank.
Solution?
 
Most likely culprit is the joker valve. They're cheap and easy to replace; I replace the one on my boat every year.
 
If you don't already have it, consider also the twist-and-lock pump, which can be retrofitted to toilets from the last two or three decades. It presses the lower flap valve down to help it seal when not in use.

Pete
 
prv said:
If you don't already have it, consider also the twist-and-lock pump, which can be retrofitted to toilets from the last two or three decades. It presses the lower flap valve down to help it seal when not in use.

Pete
Click to expand...

But it doesn't improve the backfilling - that's the joker valve. I also change ours about once a year - I have removed the limescale and put it back, but they are cheap enough that it seems simpler to make it one five minute job chucking the old one out and putting a new one back in again. A couple of things though - I have had brand new joker valves which are not watertight and you can tell this by holding them up to the light and seeing if any light shines through. Secondly the height of the water in the outlet pipe - up to swan neck or holding tank - helps keep the joker valve closed so if your pipe hardly rises at all then you might get some drips through.
 
I have a Jabsco Lite that does not have a foot valve but the joker valve needs to be cleaned several times per season when the bowl back-fills. Main reason for this is the very low flush volume as needed for gravity holding tanks. A full flush every time will keep the joker valve clean.
 
I'm trying to picture that which I can for the inlet valve and can't quite for the outlet, but we have Twist and Lock on 3 heads and they will all flood copiously in the twisted and locked position if the joker valve is stuck open for some reason so my experience has been that Twist and Lock seems to do very little.

Edit: Just thinking a little longer about this. As replacing the Joker valve cures the problem completely I have not changed the top valve under the Twist and Lock in any heads for 8 years, so I may have let all the top valves become duff hence my disdain for relying on Twist and Lock. Next time I need to change a joker valve I will temporarily change the top valve instead and see whether that solves the problem. Then of course change the joker valve anyway for belt and braces even if the top valve change does the job.
 
Last edited:
LadyInBed said:
I replaced my joker after 16 years! I had a hell of a job getting the new one to line up and seal. I will need to let the memory fade before I do it again.
Click to expand...

I had exactly the same problem the first time and took me an hour to get it right. But 20 ish times later it takes about 5
minutes with the seal feeling exactly right or not by holding it rather than waiting until you’ve done all the awkward screwing.
 
RupertW said:
Edit: Just thinking a little longer about this. As replacing the Joker valve cures the problem completely I have not changed the top valve under the Twist and Lock in any heads for 8 years, so I may have let all the top valves become duff hence my disdain for relying on Twist and Lock. Next time I need to change a joker valve I will temporarily change the top valve instead and see whether that solves the problem. Then of course change the joker valve anyway for belt and braces even if the top valve change does the job.
Click to expand...

The twist and lock doesn't do anything for the valves at the top, which are for the inlet side anyway and the OP's bowl is filling up from the outlet.

The twist-and-lock pump handle locates under a sort of bayonet fitting on the top of the pump housing, so that the piston is held fully down. The piston has a sort of "finger" on the bottom which, when fully down, presses onto the large bottom flap valve and should hold it closed.

The joker valve is the main thing for holding up the water in the loop; I just mentioned the twist-and-lock because Jabsco apparently think it helps.

Pete
 
prv said:
The twist and lock doesn't do anything for the valves at the top, which are for the inlet side anyway and the OP's bowl is filling up from the outlet.

The twist-and-lock pump handle locates under a sort of bayonet fitting on the top of the pump housing, so that the piston is held fully down. The piston has a sort of "finger" on the bottom which, when fully down, presses onto the large bottom flap valve and should hold it closed.

The joker valve is the main thing for holding up the water in the loop; I just mentioned the twist-and-lock because Jabsco apparently think it helps.

Pete
Click to expand...

I'm not sure why you seem to mistrust the concept of the twist and lock mechanism? Both our toilets suffer leakage from the holding tank riser back past the joker valve to some degree if the twist and lock is left unlocked. However, if the twist and lock is locked, both bowls stay empty.

I assume this is because the bottom flap always get clear water flushed past it even if only a few pumps are used, whereas the joker valve is more likely to reside in black water and therefore suffers more from contamination build-up on the sealing surfaces.

Richard
 
A couple of informative videos

How the manual pump works


Diagnose waste water backflow

 
Although the joker valve is the prime suspect, I don't think that it is proven that the filling is back-filling. If the bowl fills with the lever in the 'dry' position, then back-filling is the reason, but if the lever is left in the 'wet' position, then syphoning can occur on the inlet side too.
 
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