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Old 21-03-2015, 09:22   #1
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Macerator pump doesn't suck.

I have a challenge on my Morgan 383. The holding tank is in the keel and as such is below the macerator pump. The macerator pump can pump out what is in the waste lines but can't pump the tank. I'm reasonably confident that this is due to the waste line from the head, same line as the macerator is tied in to, being a standpipe that does not reach into the tank but stops at the top of the tank so no waste can be sucked up.
After many hours of sleeplessness and trying to figure this out here's what i'm thinking of doing to solve the issue. If I can find a suitable pipe (ABS or SS) I can feed it through the input fitting on the top of the tank. I would leave it long enough that it is a few inches of the bottom of the tank. Then I would reattach the input line clamping the standpipe and the pipe so i have a tight seal.

The other option though not as clean and requiring much more plumbing in cramped and inaccessible spaces is to connect the macerator to the pumpout line. (not the preferred option).

Looking for feedback as to anyone else having a similar issue and solutions or just a gut check if this sounds feasible.
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Old 21-03-2015, 13:04   #2
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Macerator pump doesn't suck.

Quote:
Originally Posted by wolfesmy View Post
I have a challenge on my Morgan 383. The holding tank is in the keel and as such is below the macerator pump. The macerator pump can pump out what is in the waste lines but can't pump the tank. I'm reasonably confident that this is due to the waste line from the head, same line as the macerator is tied in to, being a standpipe that does not reach into the tank but stops at the top of the tank so no waste can be sucked up.

After many hours of sleeplessness and trying to figure this out here's what i'm thinking of doing to solve the issue. If I can find a suitable pipe (ABS or SS) I can feed it through the input fitting on the top of the tank. I would leave it long enough that it is a few inches of the bottom of the tank. Then I would reattach the input line clamping the standpipe and the pipe so i have a tight seal.



The other option though not as clean and requiring much more plumbing in cramped and inaccessible spaces is to connect the macerator to the pumpout line. (not the preferred option).



Looking for feedback as to anyone else having a similar issue and solutions or just a gut check if this sounds feasible.

Not sure why the plumping is tied together this way.
Is your head an electric/macerating type?
Not understanding why the Macerator pump is tied into the waste line of the toilet, if it's not an electric type.
Macerator are usually 1 1/2" input to the pump, and 1" output to the holding tank input line, which is not usually a stand pipe, but stops at the top of the tank.
Could you explain further so I'm not shooting in the dark?
How is the holding tank pumped out?
Macerator inline to tank discharge line, on to Y valve, then to OVB, Or deck Pumpout.
Or sucked out by Pumpout suction?
Or is the Macerator just to liquefy the toilet contents, and empties into holding tank inlet.

A lot of folks use a Macerator to empty the holding tank, but it's not a great design.
As the Macerator can break for a number of reasons, then you have what's left with no way to pumpout.


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Old 21-03-2015, 14:29   #3
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Re: Macerator pump doesn't suck.

The macerator plumbing must have a tube to suck from the bottom of the tank to be able to suck the tank empty.
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Old 22-03-2015, 05:44   #4
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Re: Macerator pump doesn't suck.

I had the same issue years ago. Impeller style pumps are supposed to be able to draw from around 4 feet height but in my experience they are unreliable if not primed, especially with a bit of impeller wear or broken vanes. Unless you can confirm your plumbing is actually as you describe it would have to be considered doubtful because it would never have worked. I built a holding tank for my boat using top drawing and in thinking about it, it would look as you are describing, but it does have a draw tube in the tank. Anyway, if you find you have the tube and the problem is the pump height, the ultimate solution is a diaphragm macerator pump to replace the impeller version.
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Old 22-03-2015, 07:45   #5
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Re: Macerator pump doesn't suck.

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... the ultimate solution is a diaphragm macerator pump to replace the impeller version.
The macerator on my boat is a diaphragm type w/ a single set of joker (duckbill) valves.

The vacuum generator on my Vacuflush system has two sets of joker valves.

The entire systems continues to work fine w/ normal maintenance and cleaning.
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Old 22-03-2015, 07:59   #6
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Re: Macerator pump doesn't suck.

I have a 12V. air pump to air up my dinghy. You know the type, lots of volume and low pressure. I cut my vent line and reconnected it with a barbed connector. When I want to empty my holding tank I get the valves set for overboard discharge then add a low air pressure to the holding tank thru the vent line. Empties my holding tank in one minute and 43 seconds!
I shudder to think what might happen if the "Y" valve was set to connect the toilet to the holding tank and the "joker valve" failed!
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Old 22-03-2015, 09:36   #7
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Re: Macerator pump doesn't suck.

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When I want to empty my holding tank I get the valves set for overboard discharge then add a low air pressure to the holding tank thru the vent line. Empties my holding tank in one minute and 43 seconds!
Very clever!!!

Please alway have someone standing-by, video recording the process, in-case something interesting happens, so the video should then be posted on-line for everyone else's entertainment.
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Old 22-03-2015, 11:26   #8
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Re: Macerator pump doesn't suck.

Quote:
Originally Posted by Reefmagnet View Post
I had the same issue years ago. Impeller style pumps are supposed to be able to draw from around 4 feet height but in my experience they are unreliable if not primed, especially with a bit of impeller wear or broken vanes. Unless you can confirm your plumbing is actually as you describe it would have to be considered doubtful because it would never have worked. I built a holding tank for my boat using top drawing and in thinking about it, it would look as you are describing, but it does have a draw tube in the tank. Anyway, if you find you have the tube and the problem is the pump height, the ultimate solution is a diaphragm macerator pump to replace the impeller version.

I'm pretty sure these diaphragm waste pumps are not macerators, they evacuate waste from the tank with no grinding.
They are simply waste transfer pumps.



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Old 22-03-2015, 11:32   #9
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Re: Macerator pump doesn't suck.

If it's a dip tube type tank, it's either fallen off or is clogged at the bottom, I've replaced tanks where this was the case, stuff accumulates at the bottom.
Rapidly if not emptied promptly, and allowed to sit.


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Old 22-03-2015, 12:17   #10
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Re: Macerator pump doesn't suck.

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Originally Posted by wingless View Post
The macerator plumbing must have a tube to suck from the bottom of the tank to be able to suck the tank empty.
Yes. I would hope anyone with a bit of sense would understand that.

If the outlet from the tank is a dip tube and it doesn't reach to within an inch or two of the bottom, it has broken off and is laying in the bottom of the tank.

Of course it's possible that a previous idiot confused the outlets and this is actually the inlet from the head.

The basic principal of a holding tank is, the poop goes in at the top and comes out from the bottom. This can be a dip tube, one or more outlets near the bottom, or one outlet near the bottom and a "Y" fitting to provide for either a macerator pump to overboard or a deck fitting for a marina pumpout.
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Old 22-03-2015, 15:27   #11
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Re: Macerator pump doesn't suck.

Quote:
Originally Posted by Boatyarddog View Post
I'm pretty sure these diaphragm waste pumps are not macerators, they evacuate waste from the tank with no grinding.
They are simply waste transfer pumps.



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Yes, that is correct and I should have noted that. If there is a legal requirement to macerate and the heads aren't electric macerating types then the diaphragm pump would not be legal by itself. Legalities aside, waste from a holding tank exits very mashed up even if un-macerated and passed through a diaphragm pump (don't ask me how I know!).
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Old 22-03-2015, 15:39   #12
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Re: Macerator pump doesn't suck.

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Originally Posted by Reefmagnet View Post
Yes, that is correct and I should have noted that. If there is a legal requirement to macerate and the heads aren't electric macerating types then the diaphragm pump would not be legal by itself. Legalities aside, waste from a holding tank exits very mashed up even if un-macerated and passed through a diaphragm pump (don't ask me how I know!).

Nuff said there, my friend.😝


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