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Old 16-06-2016, 13:56   #1
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Strong Back Pressure in the Head

We are on Day 2 of our cruising life. Left Beaufort, SC yesterday and we're in Charleston, SC today. Jabsco manual pump. Strong back pressure when pumping down. Nothing leaves the toilet. Got a pump out when we arrived in Charleston. Took the pump apart and cleaned it. Shoved a hose down the pump out deck fitting and filled until water came gushing out of the deck fitting and the vent, so vent seems to be clear. While this was going on, no water came into the boat by way of the line from the toilet to the tank (which was disconnected from the hand pump). Sprayed water into the line from toilet to tank (still disconnected from pump). Put everything back together, still strong back pressure, maybe even worse. Please help! My wife and two girls (3 and 4) are off to the pool, I need to get this fixed! Does it sound like something is clogging the line from the toilet to the holding tank? That's what I suspect, but I fear that situation because tracing that line to the tank and disconnecting it will require ripping the boat apart.
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Old 16-06-2016, 14:05   #2
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Re: Strong Back Pressure in the Head

Trace the lines from the toilet.

I'd suspect a Y valve set to the direct overboard setting and the thru-hull is closed.

If not that, you've got a crappy job ahead of you - the discharge hose from the head to the tank is clogged, or the joker valve is stuck closed (I really don't think that can happen), or the valve at the bottom of the pump is stuck.
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Old 16-06-2016, 14:44   #3
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Re: Strong Back Pressure in the Head

I should add that I don't believe this boat is set up with a y valve at all. I think the toilet pumps straight to the tank, and then you can can either pump out the tank through the deck fitting or with the macerator pump.
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Old 16-06-2016, 15:28   #4
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Re: Strong Back Pressure in the Head

I think I may know what's going on, but I need a little more information to be sure.

Reconnect the flush water inlet line to the toilet....disconnect the toilet discharge hose from the toilet, then pump the toilet in both the wet and dry modes ('twould be a good idea to put a trash bag or something under the discharge fitting to catch the water)This will tell you whether your problem is in the toilet or in plumbing downstream of the toilet. Then tell me whether it works--or not--in either or both modes.
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Old 17-06-2016, 09:45   #5
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Re: Strong Back Pressure in the Head

Sounds like a clogged toilet outflow line. You might try a snake from the tank to the toilet befor anything more radical. You can get deposits built up in the lines. At worst you should be able to disconnect both ends ans slide the hose free to clean our or replace. I don't think ripping out bulkheads should be necessary.
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Old 17-06-2016, 10:05   #6
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Re: Strong Back Pressure in the Head

Check to see if the vent on the holding tank is clogged.
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Old 17-06-2016, 10:06   #7
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Re: Strong Back Pressure in the Head

Nope...not a clog and if you read his second post you'll see that he'd already eliminated a blocked tank vent. We ID'd the problem on the phone this morning.

Best way to determine whether a problem is in the plumbing or the toilet is to do what I recommended in my previous reply--disconnect the discharge line from the toilet, put a plastic bag under the fitting to catch the spill and flush the toilet in both modes. If it works fine, the problem is downstream. It didn't when he did it...it worked fine in the wet mode, but not in the dry mode. And that confirmed what I suspected...

Jabsco manual toilets have had a common problem for years. The wet/dry "valve" is a cam (little "gate") that the lever swings to block or unblock the flow of incoming flush water. Due to a mfr'g, design or tooling defect, that cam hangs up...creating what feels like back pressure in the dry mode. The only cure: replace the wet/dry cam assembly--which requires taking the pump apart--or replace the pump, which only requires removing and replacing 4 bolts and 2 hoses. He went shopping for a new pump after we talked this morning.
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Old 17-06-2016, 10:15   #8
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Re: Strong Back Pressure in the Head

Ha! You beat me to it. peghall. That little cam gizmo is a hidden screwup waiting to snap. Used to be an el shapped lever that failed . Once caught a little cod fish that jammed it and caused the same effect.
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Old 17-06-2016, 10:57   #9
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Re: Strong Back Pressure in the Head

Had same problem , pump pressure into tank , go to deck waste fitting unscrew ,if you hear air escape , vents could still be clogged . clean out with wire , also threw hull fitting could have screen in it that needs to be removed . Hoses to tank get build up in them , remove them , take to dock and beat on them with hammer until clear , have had to do this out at sea !! good luck and am still jealous you are fixing things in exotic places !!!
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Old 17-06-2016, 11:09   #10
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Re: Strong Back Pressure in the Head

Maybe a more simple solution: I have this problem occasionally with my jabsco manual head. I just move the lever from wet to dry a few times. It seems the gate just doesn't release properly. Once or twice back and forth and it works great, been that way for 3 years.
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Old 17-06-2016, 11:15   #11
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Re: Strong Back Pressure in the Head

When my Jabsco did the same thing it ended up been a plugged outlet hose to the holding tank from the toilet with scale. Had to pump water into it with pressure about 5 psi let go and it would bring back the scale, a few times repeat till I got it unplugged. Its a nasty job but somebody had to do it and I'm the captain. Good luck Captain
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Old 17-06-2016, 11:17   #12
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Re: Strong Back Pressure in the Head

I read this all wrong. I thought you had a strong back and pressure in your head.
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Old 17-06-2016, 11:56   #13
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Re: Strong Back Pressure in the Head

Quote:
Originally Posted by sailorchic34 View Post
Check to see if the vent on the holding tank is clogged.
Double ditto on this. It happened to me. And when the tank was pumped out it almost collapsed from the strong vacuum. I rebuilt the vent to make it harder to plug in the future (put a bigger 3/4" vent in and put it on the top of the tank instead of on the side where it was guaranteed to plug.
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Old 17-06-2016, 11:56   #14
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Re: Strong Back Pressure in the Head

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Old 17-06-2016, 13:23   #15
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Re: Strong Back Pressure in the Head

some of those gaskets/valves have been known to be assembled the wrong way round during "maintenance"...
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