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Old 07-11-2018, 10:49 AM   #1
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Oldersalt's Avatar
City: San francisco
Country: USA
Vessel Name: Pacific Star
Vessel Model: 1990 Grand Banks 32 #834
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Holding Tank Question--Peggie Hall?

With the Y-valve in either position, hitting the macerator pump just seems to blow bubbles out of the overboard (below water line) pumpout line. With Y-valve in "deck" position the dock-based pumpout machine seems to pull contents out just fine.

But up here in Canada I really need to be able to pump overboard. I can't figure out why I can't pump overboard.

If the tank contents are prettly low, could it just be sucking air from the vent line? But why would it blow bubbles in both positions? Or have I destroyed the macerator pump?

1990 Grand Banks 32. Raritan SeaEra electric toilet with fresh water flush. Standard Johnson (?) macerator pump.
Standard plumbing as far as I can tell.
25-gallon tank
toilet empties into bottom of tank.
air vent at top of tank goes to just above the waterline
Deck pump-out draws from top of tank thru Y-valve
Overboard macerator pump draws from top of tank to outlet just below waterline

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Old 07-11-2018, 11:29 AM   #2
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City: Litchfield, Ct/Punta Gorda, Fl
Country: USA
Vessel Model: Atlas Pompano 23
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Is the Y valve really moving when you turn the handle. What you describe sounds like the Y valve is stuck half way between the two positions so the macerator pump is pulling air from the deck fill and/or the vent.

Or as a less likely cause, the ball in the Y valve is severely corroded allowing air to be pulled through the macerator in either position.


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Old 07-11-2018, 12:40 PM   #3
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I agree it sounds like a valve or maybe air leak issue, but I imagine it could also be a problem with the macerator pump - for example the impeller may have failed.
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Old 07-12-2018, 10:15 AM   #4
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City: Maryland
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We had a blockage on the macerator discharge from our fish box. Build up from years of fish scale and so forth... The macerator worked, but nothing passed. Removing the discharge hose from the thru-hull and chipping away the fish bits opened the line, all began working again after we reinstalled the hose.

South River, Chesapeake Bay
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Old 07-12-2018, 11:37 AM   #5
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City: AR
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From the information you gave me on the phone yesterday, it appears you have two problems: 1. a y-valve that isn't closing the overboard outlet completely--and therefore may not be opening the pumpout outlet completely either--and...2. A fried or otherwise failed macerator impeller. You did say you've allowed to it run dry several times.
I recommended that you do two things: replace the macerator impeller and open up the y-valve to find out what's interfering with it's ability to rotate completely...could be sea water mineral and/or waste buildup or even something as small as a grape seed. Or, although unlikely, a defective y-valve.
Looking forward to getting an update on the results!

"If you can't explain it to a six year old, you don't completely understand it yourself." --Albert Einstein
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Specializing in marine sanitation since '87.
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