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Old 22-05-2008, 09:27   #1
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Head Back Flow

Last year we had a problem with our head either emitting a foul odor or, when sailing, backing up and filling the bowl. It's set to dry flush. The boat and the Jabsco head are one year old. I read on a blog somewhere that an owner with the same problem suggested that the issue was with the joker valve (the rubber valve type thing that is supposed to prevent backflow) which is made of a softer rubber in the Jabsco head than some of the other models on the market. Apparently the problem is 'created' by the fact that the holding tank, which is located higher in the boat than in many others, increases the backwards pressure on the joker valve. I seem to recall reading in the blog that someone had gone out and purchased a joker valve of the same size but made with a stiffer rubber from another head manufacturer and reported that it had fixed the problem. I'm not sure if that's really the problem or the solution but that's what I recall reading.

I sent an e-mail to Jabsco outlining the problem. While they didn't acknowledge the problem or comment on the fix I'd read about, they did recommend that we replace the original "gray" handled pump assembly (29040-2000) with a newer "twist-lock" dark blue handle pump assembly (29040-3000). The twist-lock version "allows the pump to block the water coming back from the holding tank."

I was wondering if anyone else has had the same issue and what your experiences/fixes have been.
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Old 22-05-2008, 09:47   #2
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I had a similar problem with a Raritan head. In the case of the Raritan it is the joker valve being deformed which allows the backflow. I was ready to trash the durn thing. The trick to fixing it according to head guru Peggy Hall is to not overtighten the flange that contains the joker valve. In my last rebuild I was lucky and got it just right - no backflow.
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Old 22-05-2008, 10:42   #3
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you'd be shocked to see how little protection you have to seawater filling your bowl then your boat by the lever being in the 'dry' position. Most folks who end up having a boat sunk because of the failure of the valve end up closing the intake seacock when not in use. You might consider it!
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Old 22-05-2008, 12:03   #4
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Hi Randy,

Valid points - a shut seacock is the safest - most of us rely on an anti-siphon loop to prevent sea water backflow.

However, I think what he is referring to is that last bit of stinky liquid that remains in the hoses and doesn't make it to the holding tank/discharge. In mine there would always be a quart or two that wouldn't make it. The joker allowed that to gradually seep back into the bowl and stink up the boat.
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Old 22-05-2008, 17:30   #5
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Mine's done this. The seacock stays closed unless we're offshore and discharging directly into the sea. My sink has done this as well on a hard beat.
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Old 22-05-2008, 18:17   #6
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The joker valves start leaking back in very short time in my experience and probably not unexpectedly so given their simple construction. They are particularly prone to losing their sealing ability if someone pumps hard against a blockage so building up back pressure which then inverts the joker valve inside out when pumping is stopped - it is the pushed right way around again next time normally pumped with solids (hopefully ).

In our own case we don't worry about the condition of the joker valve too much as we took the inlet to the holding tank into the top of the tank. We take care to pump enough so that there is only clean sea water left in the pipe lift to the top of the holding tank or, if discharging overboard, to the top of the siphon break.

For us, if a new joker valve is not fitted, we get about 1/3 of the bowl fill with sea water back flow in the worst case (worst case being from the lift in the antisiphon loop if overboard discharging, the lift to the top of the holding tank is much less).

So, maybe it is possible to change to a top entry on the holding tank or, more simply, rearrange the pipework so that the pipe to the holding tank rises above the level of the tank top at some point between the toilet and the tank and so can only drain back what is on the toilet side of the rise.
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Old 06-09-2012, 11:22   #7
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Re: head back flow

I have the same problem with two new Jabsco heads, both with the new "twist-lock" handles. My holding tank is above the head, but fortunately it fills from the top of the tank, so the backflow is limited to the residual liquid in the hose. Still looking for a solution...
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Old 06-09-2012, 11:47   #8
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Re: head back flow

Quote:
Originally Posted by emersonb View Post
I have the same problem with two new Jabsco heads, both with the new "twist-lock" handles....Still looking for a solution...
I also have problems with the newer twist-lock version. My old one was working fine, but the housing got cracked, as they are prone to do, so replaced with the "new and improved" version -- not impressed.

I read that Raritan has better quality manual pump which is a drop in fit to replace the Jabsco. Think I will try that next.
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Old 06-09-2012, 11:53   #9
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Re: Head Back Flow

If you have a link to the Raritan replacement pump, can you post the link? I may give that a try also.

Thanks!
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Old 06-09-2012, 12:00   #10
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Re: Head Back Flow

Aaaahh ..... the joys of fixing head problems!

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Old 06-09-2012, 12:55   #11
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Re: Head Back Flow

HOLY ****!!!!!!!!!!!!!!
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Old 06-09-2012, 12:58   #12
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Re: Head Back Flow

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Originally Posted by emersonb View Post
If you have a link to the Raritan replacement pump, can you post the link? I may give that a try also.

Thanks!
Don't have a link but think I saw it discussed here on CF.
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Old 02-04-2013, 01:43   #13
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Re: Head Back Flow

Am having this self-same issue. Found this review of the Jabsco replacement pump assembly:
Jabsco Manual Pump Assembly For 29090-Series - 29040-3000 - BoatersWorld.com

I just paid the $50 or so bucks for the rebuild kit. I may not have been all that cautious ala cabo and Peg Hall about replacing the joker valve with the appropriate amount of finesse. It seems like the kit stopped the backflow for a while, (2 months?) but I am back to seeing the bowl fill with black water.
Anybody else have luck with the Twist 'n' Lock? Any other solutions?
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Old 02-04-2013, 02:38   #14
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Re: Head Back Flow

Interesting to see this old thread revived again.

I have two Jabsco electric conversions, and they both slowly leak back as well. I have not yet pulled them down to check them. But I do need to replumb the system, and would like to reduce the volume of blackwater that gets left in the pipe between the pump and holding tank.

What is the smallest diameter pipe I can fit to keep that volume to a minimum, yet not risk blockages?
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Old 02-04-2013, 09:30   #15
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Re: Head Back Flow

I've eliminated this problem by getting rid of my old head that used a joker valve and replacing it with a Lavac which uses a remotely mounted Henderson 5 diaphragm bilge type pump. Both of my old heads seemed to have this issue to some extent.
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