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alanrothenbush 05-15-2011 07:40 PM

Macerator or diaphram pump to empty holding tank?
I'm in the middle of adding a holding tank to my Windward 850 and now have a decision to make; what kind of pump to use.

I was planning on a macerator pump; no real chance of clogging, the output finely shredded and so on. I even bought one.

But it just occured to me that unless the pump is higher than the seacock/throughhull (which it won't be), there will be sewage left in the line. This just sounds like a bad idea.

I would think that a diaphram style pump would be able to "pressurize" the line and therefore pump everything out, making it the better choice.

Am I missing something?

Thanks for any thoughts.


Maine Sail 05-15-2011 07:45 PM

Manual pumps are generally more reliable but should ideally keep 1 1/2" all the way to and including the thru-hull. Most 12V macerators are a 1" outlet. The line will be full anyway. If the tank is full liquid always levels itself and the drain line is off the bottom of the tank unless you tank uses a dip tube design..

alanrothenbush 05-15-2011 10:49 PM

Thanks for the reply!

You're correct, the pump outlet is a 1" line.

I've heard everywhere that waste sitting in the hoses is (eventually) a major source of odor and so I'm trying to do everything to keep the hoses empty.

The outlet of my tank is down at the bottom. I'm using all brass fittings from tank to ball valve to pump.

So any sewage up to that point sitting around will be sitting in brass; no smell there.

But the 1" line from the pump to the anti-siphon "U" tube will be full, won't it?

I'm now heavily leaning to a Whale Gulper ...


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