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Old 21-01-2014, 04:53   #1
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Jabsco Manual Head Question - Could be user error

So I'm new to this whole owning a boat thing and am working my way through various problems. I own a new boat, as in I picked her up from the manufacturer 3 months ago. I was expecting at least a little bit of repair free time, but I might have my first head issue.

Issue: Head fills with liquid when not in use.

I have confirmed that it is not raw water filling the head, but waste water. It fills to about 1 1/2 inches below the seat so I'm a little nervous. I assume it is stopping there because either a) that's approximately the water line, or b) that just happens to be the amount of liquid in the waste tube that gravity pulls back into the bowl. I'm leaning towards A.

What I've done:
I've closed the intake seacock and pumped the head dry. I leave the switch next to the head at "DRY" and lock the pump handle down. At that point the head will start to make gargling sounds and after a while will fill back with water.

I assume this means I have a blocked value or something. Any ideas on what I can do to see what is wrong?

I also realize this could be something stupid and user error. I would love for that to be the issue actually.

Thanks in advance!

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Old 21-01-2014, 04:58   #2
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Re: Jabsco Manual Head Question - Could be user error

Failed joker valve most likely


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Old 21-01-2014, 05:18   #3
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Re: Jabsco Manual Head Question - Could be user error

Yup I agree with Dave...the head is filling to the waterline and you need to repair the joker valve.
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Old 21-01-2014, 05:50   #4
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Re: Jabsco Manual Head Question - Could be user error

The twist lock handle model that the OP describes actually pushes and holds the flapper valve down to prevent backflow. Even if the joker valve is bad, this prevents backflow.

My guess is that the flapper valve is either bad or unseated a bit. The joker valve could also be bad and need replacing, but the waste is getting back through the locked flapper valve.

In the US, a complete new pump body for that model (basically the whole head except the bowl) only cost ~$60 and is cheaper than the rebuild kits and removes the guess work.


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Old 21-01-2014, 13:36   #5
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Re: Jabsco Manual Head Question - Could be user error

Does the toilet have a anti siphon venting loop?

Agree with others that the toilet is filling to outside water level and if it's a new boat take it back,alternatively as already suggested don't mess just replace the whole pump assembly, BUT, you may still need an anti siphon set up.
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Old 22-01-2014, 10:45   #6
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Re: Jabsco Manual Head Question - Could be user error

Sounds like a blocked holding tank vent is causing pressure to build up in the tank.
When this happens, it can push sewage right back through the joker valve.
Be very careful opening the deck pump out fitting. You might get a nasty surprise.

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Old 24-01-2014, 07:29   #7
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Re: Jabsco Manual Head Question - Could be user error

I think previous posters have diagnosed the problem correctly but want to comment on something you mentioned and that is the toilet fills to about 11/2 half inches below the rim. That's a nice thing to know about your boat!

I once had a boat that came with old heads that I soon replaced (actually just removed one of them) and I wanted to see what would happen if my joker valve failed someday. So, I opened the valve and let the head sloooowly fill until the water finally reached the rim, not good. So, I cut and routered the edges of a couple of layers of starboard plastic and inserted them beneath the head to raise it about an inch. Then, I once again tried my little experiment and the head only filled to about 1/2" below the rim before the water stopped rising. I added one more piece of starboard for good measure and had greater peace of mind because I knew that a failed valve or seal could no longer sink my boat.

The reason I happened to think of doing this was that one calm, peaceful Sunday morning a few years earlier, while dinghying in to the dock from my previous boat, a Hinckley Pilot 35, I happened to notice another Pilot 35 in the harbor that was looking VERY sleek, almost like it had been actually took a few seconds for me to realize that yes, it actually was a boat identical to mine..... and I couldn't see the boot stripe! Numerous boats were coming and going in the main fairway of the harbor within 50' of this boat, oblivious to the fact that it was slowly sinking right in front of them! I think the only reason I happened to notice what was actually happening was that I happened to have an identical boat so was very familiar with exactly how it should look. So, I climbed aboard and fortunately the companionway was unlocked but the settee cushions were already afloat so none of the thru hulls were visible, but because they were located in the identical position to the thru hulls on my boat I was able to find them and close them all so the boat didn't actually sink. I called the nearby Coast Guard station and the local marina and they both showed up with a big pump that quickly had her floating back on her lines. Work intruded so I wasn't around the harbor much for the next couple of weeks. My mooring was one of the furthest ones in the very outer reaches of the harbor and it was very gratifying about 3 weeks later to answer a knock on the hull of my boat to see this eighty something year old guy (turns out he was quite wealthy and the Pilot 35 was his daysailor) in his little rowing dinghy who was there to personally thank me for saving his boat. Apparently someone had told him I was the one who did it and he had been rowing all the way out almost daily to attempt to thank me.
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Old 03-02-2014, 08:30   #8
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Re: Jabsco Manual Head Question - Could be user error

Wow, thanks everyone for all of the replies and advice. Their was a Lagoon shop right near where I was and after bringing them over and showing them what was happening they replaced the entire pump for free given how new the boat was. As some of you mentioned it was still a good process to go through. Now I know that assuming I don't weight her down much more that the rim of the head is above the waterline.

Fixed for now and I appreciate everyone's input.


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head, jabsco

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