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Old 05-28-2013, 01:59 PM   #1
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Macerator pump fixed, for now

Last weekend my macerator pump locked up. It would draw about 50 amps (normal is about 20) when I turned it on and then trip the breaker.

Replacing the pump isn't a chore to be taken lightly, so I tried a few tricks first before pulling and replacing it and one worked.

I first pulled off the discharge hose and while a bit of s*** dribbled out from the holding tank through the pump. I tried to work a screw driver down in and wiggle the impeller. I coulnd't tell if anything was moving when I did this, but the fact that stuff dribbled back out told me that it wasn't a clog of toilet paper or ???. But when I tried the breaker again, same thing.

So I clipped the connectors near the pump and then reversed the power leads. The pump buzzed but didn't move when I applied power. I thought that this was a dead end, but when I rehooked up power with the correct polarity, it worked.

But who knows for how long.

David
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Old 05-28-2013, 09:08 PM   #2
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If is a jabsco there is a slot in the end of the motor for a screwdriver to manually rotate the shaft
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Old 05-28-2013, 09:22 PM   #3
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At the end of last season, my macerator pump began tripping the breaker. I took it apart and found that one of the rubber "paddles" on the elliptical pumping surface of the rubber wheel had broken off and jammed the shaft. Replaced the rubber paddle-wheel and all has been well since.

My point is that you may have gotten your pump to move by freeing the obstruction, but if it was one of the rubber paddles that broke off, and has now been dislodged, you may find that the pumping action is not all it should be. Those units will spin even with all the paddles worn or broken off, but they won't pump worth a darn. You might want to pull it apart for a look before you *really* need it.
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Old 05-28-2013, 10:19 PM   #4
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If is a jabsco there is a slot in the end of the motor for a screwdriver to manually rotate the shaft
^+1. What make of pump is it?
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Old 05-29-2013, 01:21 PM   #5
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That slot in the shaft has helped me unblock mine twice now turned it back and forth a few times and it came free.
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Old 05-29-2013, 01:55 PM   #6
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It is a Jabsco, but I don't remember a slot on the motor end. I will have to look harder. That is a whole lot easier than reconnecting wires to unjam the pump.

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Old 05-29-2013, 02:15 PM   #7
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These pumps have always made me sick (in more ways than one) and over the years I have always eliminated them from my boats by using a 3 way valve and a aft facing clamshell over the underwater discharge.
Position 1 head to discharge.
Position 2 head to tank.
Position 3 tank to discharge.
Depending on the height of your holding tank and the speed of your boat, the forward motion will empty your tank quickly.
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Old 06-05-2013, 10:57 PM   #8
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The impeller in a macerator pump should be replaced as PREVENTIVE maintenance at least every two years. Why? Because...

1. The second or two that it runs dry when it's first turned on is enough to wear a miniscule amount off the edges of the vanes each time...wear that's even, so it isn't visible to the naked eye, but gradually reduces the efficiency of the pump till finally the impeller can no longer impel anything through it.

2. Waste is sticky...the pump and discharge line SHOULD be rinsed out after each tank dump, but nobody ever does. So the impeller vanes stick to the inside of the housing...and startup can put enough enough stress on the vanes to crack at least one, or even break one. And when that happens, the impeller will no longer impel anything.

No one ever finds out that the macerator pump doesn't work when the tank is empty...only when they try to dump a full tank and can't. Replacing the impeller as preventive maintenance allows you to do it at a convenient time when the tank is empty so that will never happen.
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Old 06-06-2013, 06:47 AM   #9
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.t"he pump and discharge line SHOULD be rinsed out after each tank dump, but nobody ever does. So the impeller vanes stick to the inside of the housing...and startup can put enough enough stress on the vanes to crack at least one, or even break one. And when that happens, the impeller will no longer impel anything."

A better quality macerator pump like a Galley Maid will have a water feed that helps liquify the discharge and lubricate the unit.

Probably 5 X the price of RV / "Marine" units , but worth it if messing about with waste pumps is not big in the cruising plan.
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Old 06-07-2013, 08:03 AM   #10
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It is a Jabsco, but I don't remember a slot on the motor end. I will have to look harder. That is a whole lot easier than reconnecting wires to unjam the pump.

David
On mine there is a plastic plug covering the screw slot that must be pryed off.
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Old 06-07-2013, 08:06 AM   #11
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2. Waste is sticky...the pump and discharge line SHOULD be rinsed out after each tank dump, but nobody ever does.
Actually I do. I rigged a simple system where I suck about 1 gallon of water out of a bucket thru the pump only.
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Old 06-07-2013, 09:26 AM   #12
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1. The second or two that it runs dry when it's first turned on is enough to wear a miniscule amount off the edges of the vanes each time...wear that's even, so it isn't visible to the naked eye, but gradually reduces the efficiency of the pump till finally the impeller can no longer impel anything through it.
If the vanes were perfectly straight out from the hub, that is if they had no contact loading induced by the flexure required to fit the impeller inside the ID of the pump body (which is less than the OD of the impeller) that might be true. But even then only true until that miniscule bit of wear matched the ID of the pump body. Once that happened there would be a microscopic clearance, and no more wear. That microscopic clearance would be no different than any other pump with parts moving in relation to fixed parts.

Considering that the pumping action of a flexible impeller pump is created by the increase in volume between the vanes produced as they pass the inlet and decrease as they approach the outlet, all the vanes do in between is sweep the fluid around the arc. As long as there is enough vane and enough flexibility left to provide contact between the vane and the body, fluid will move.

Has anyone ever seen a Jabsco pump that had the "bulbs" on the end of the impeller worn off?
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Old 06-07-2013, 09:36 AM   #13
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I have never seen rubber vanes ineffective due to wear...only broken.

I have actually worn a hole through the side of a bronze salt water pump from sand ingestion before the rubber vanes wore badly/stopped pumping.

My boat has 3 identical macerators in use (1 for each head, 1 for overboard) and one spare. Figure I can mix and match as needed till I can get around to rebuilding the broken one.
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Old 06-07-2013, 10:50 AM   #14
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I have a bellows type macerator pump (Sea Land brand) that was on the boat when I bought it 8 years ago. I've never had a problem with it, nor have I done any maintenance on it. On my previous boat, I had an impeller type MP and I carried a spare unit. When there was a problem, I just swapped pumps. I would then repair the faulty one for the next swap. Maybe a switch to a bellows type is in order for those having issues. Especially when the MP is in a hard to reach area for maintenance.

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Old 06-08-2013, 06:50 AM   #15
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The problems we have had with diaphram pumps is both inlet and exhaust valve must be perfect to have the pump work.

Paper and waste seems to keep the seals from being perfect , even when rinsed with FW after use.

Perhaps if the pump was lower than the waste , it would operate with out the need to lift and being immersed less prone to buildup.

But replacing/repairing it could be loads of fun.Long intake and discharge hose , so you could lift it to drain might work.

We have found that unless the pump is $uper (Obendorfer or Galley Maid) the 120V macerators last lots longer than the 12v versions.
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Old 06-08-2013, 06:58 AM   #16
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I have a bellows type macerator pump (Sea Land brand) that was on the boat when I bought it 8 years ago. I've never had a problem with it, nor have I done any maintenance on it. On my previous boat, I had an impeller type MP and I carried a spare unit. When there was a problem, I just swapped pumps. I would then repair the faulty one for the next swap. Maybe a switch to a bellows type is in order for those having issues. Especially when the MP is in a hard to reach area for maintenance.

Sealand Discharge Pump
We had one these on our last boat for 10 years and never touched it. We have the same model on Hobo now for 6 years now and have never touched it. Both boats were/are full time live aboard/cruising. Last week we left the pump on for 6 hours (forgot to set the timer). Still works fine.
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