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Old 31-03-2008, 18:18   #1
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Pressure in my head

This is the second time typing this up so you'll just have to imagine the sheer prose, wondrous humour and impeccable grammar of my lost posting...

Anyway, I have one of these Jabsco heads, believe its somewhat less than four years old and to my eye everything looks alright. We've had the boat for less a month and during this time have used the head a few times. Okay, a fair few times.

While it started of fairly stiff to pump dry it is now getting to the stage where I feel the pressure required indicates some piece of critical piping is going to burst, or a seam will split with unspeakable results.

Anyway, being the adventurous type I opened up the holding tank inspection hatch and verified the everything looks *all right* which it does in a kinda scummy and unfortunately rather smelly way (working on that - we'll see if the vinegar and enzymes added this weekend help by next weekend). The tank isn't full, flush operation on the pump proves that water flows readily into it. Pump dry operation gets some water there but it still feels like there is a load of air trapped there somewhere (very compressible).

I'm hoping this is a real easy fix, something that doesn't necessitate dismantling the whole thing. Right now I'm suspecting the Joker valve to the discharge pipe but don't understand why it would work perfectly when the pump is set to flush.

Anyone experienced something similar?
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Old 31-03-2008, 18:29   #2
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Head Job

Same thing happened to me a while ago when antifouled seawater inlet painted over grab your goggles and a 6 inch nail and unblock the sea water inlet little grate by poking nail through holes from sea water side .Not to hard to find if covered over as you know approx where to find youll feel a raised section on hull about 4 inch in diameter if water clarity isnt too good.Good luck and hope you go okay with your head job.
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Old 31-03-2008, 18:47   #3
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Hi Jacana, Wouldn't that prevent it flushing too? Flushing is fine, which is what is confusing me.
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Old 31-03-2008, 18:57   #4
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Venting your ...

I'd suggest checking that the holding tank vents are working properly.

The conventional method of checking if vent pipes are blocked may not be indicated in this case.
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Old 31-03-2008, 19:10   #5
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Boracay - I thought exactly the same thing, but this should have been covered I think with the tests I did with the inspection hatch open, operating the pump in pump dry mode was still tough (and water just dribbled into the tank rather than flowing as it does in flush mode).

Didn't check the vent directly though.
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Old 31-03-2008, 19:18   #6
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No it will still flush out its only when you try to suck the water into the bowl that the pump will feel like its building vacuum pressure another way to check is to remove inlet hose at bowl make sure you have a plug ready as its below water line then when disconnected use pump it should work then you will definately know inlet grill blocked.Still much easier to hop over side and check inlet cant you hold the admirals legs till shes unblocked it.
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Old 31-03-2008, 19:20   #7
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Just saw other advice.Because it flushes out okay your vents wont be blocked.
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Old 01-04-2008, 18:20   #8
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In my experience (owned two of them in two different boats), it's a common problem with Jabsco heads: make sure the flush control lever is all the way to either to the "flush" or the "empty bowl" position. If it's not engaged all the way, the symptom is exactly what you describe - it feels as if the plumbing is going to explode...
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Old 07-04-2008, 19:40   #9
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Thanks Beausoleil!!

That was EXACTLY the problem - neither of us were pushing through the resistance for the final 1/4 inch of handle movement. Hopefully that puts off my need for anything but basic maintenance for a while.... touch wood.
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Old 03-06-2008, 21:18   #10
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I guess I have another question wrt this head and the same lever. While the original problem was solved I want to know what position to leave the lever in while under way. Our standard proceedure was to leave the incoming thruhull closed and the selector lever to "pump dry" we were doing a little bumpy sailing a few weeks back with a fullish holding tank and got a bowl full of the nasty.

Luckily it didn't spill out as currently our shower drains straight to the bilge but it was still pretty smelly down there!

The last couple of times out we left the lever in the "almost down" position that lead me to start this thread in the first place and this has been okay but then the swell has been smaller and our holding tank almost empty.
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