Join Date: Apr 2006
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Mike, the only "proper" way to dump bilge pumps is one pump, one hose, one exit fitting. Partly to ensure they don't fight each other, partly to ensure one failure can't block it all. So it you want both to pump overboard...spring for the extra plumbing, among other things it will keep insurance surveyors happy.
I suspect that your PO rigged things this way because the lower pump does not have enough lift capacity to lift water all the way from the bottom UP to deck level so it can loop and then exit the boat. You would need to measure the distance from the bottom up to the top of your loop (and as mentioned you definitely want a high loop) and then see what kind of pump capacity you can get for it.
There will also be another drawback--that whenever the pump shuts, the "slug" of water in that large hose, making that long run all the way up, is going to drop back down into the bilge--leaving lots of bilge water.
The kludgy 2-stage design you have probably also cuts that amount of water in half. So, there are plusses and minuses, and I'd guess the PO did this compromise with them in mind. (Not really the right way to do it, but...)
If you have to use a big pump with a long run, resulting in a large slug of water coming back into the bilge, the only real way that I have heard of dealing with that is by using a second VERY small pump--designed to suck up that last inch of bilge water, slowly but thoroughly, with a small diameter hose. (Yeah, three hoses, just what you didn't want to hear.)
Well, the alternative is learn how to roll the boat quickly so it spills out the companionway.