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Adding 2nd Bilge Pump to 2011 LSV


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I know some folks on here have added a 2nd bilge pump and I'm looking for suggestions/tips for doing the same on my 2011 23LSV. I'm going to put it in the center bilge compartment under the access hatch next to the helm. I've ordered a 3/4" wye, a couple 3/4" check valves, and some hose clamps from WM to tie into the factory center tank drain or vent line. First question I have is if there is any benefit to doing one vs the other. I'm thinking the vent line gets less work and in an emergency when you're trying to drain water from the boat it would be best to have the center tank drain line fully available if necessary but maybe I'm overthinking it. Next is the wiring....I'm leaning towards tying it to the factory bilge wiring so it's controlled the same as the rear bilge pump but I'm not against wiring it separate if there is some benefit to doing it that way. If I do piggyback off the factory wiring, is it best to tie in right by the bilge pump fuse behind the panel under the throttle shown in the pic below? Lastly, any recommendation on which pump to go with? I'm thinking something similar to the factory rear pump with built-in automatic feature like the ones linked below. Also something with low amp draw if I do wire it in parallel with the rear pump. Thanks in advance for the help!

Sahara S500



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Wiring wise, if you are thinking of this as an added security measure, then you should logically run separate wiring.  Is boat left on water unattended (i.e. overnight)?  If the auto bilge system fails on the rear pump, and they are wired together, then neither is going to work.  Same for emergency situation - if one shorts, and they are wired together, then they have both shorted.  Sorry no thoughts on the other questions, i believe either way your thinking is logical.

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Is it possible to drain the center tank if you have the vent line full of water trying to go the other way? 

On thinking about it for five more seconds, the worst case is that the bilge water goes into the tank and the tank pump clears it.  When the bilge is finally empty, the vent is free to let the tank empty.  Theoretically, your original pump is also removing bilge water at the same time.

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I thought that’s what the check valves would prevent. Basically isolates the bilge flow from the ballast tank flow so they can’t backfill each other. 

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33 minutes ago, statefan said:

I thought that’s what the check valves would prevent. Basically isolates the bilge flow from the ballast tank flow so they can’t backfill each other. 

Sure, when the vent line has air in it.  The tank can't empty unless it can displace the water with air.  If air is in the vent line, the tank will empty.  If water is in the vent line, the tank will take it.  You may still get flow out the vent line if the bilge pump has higher volume than the tank pump, but the tank is still going to take its share until the bilge pump is done moving water.

Maybe it isn't plumbed like I'm picturing, but that's the way I see it.  Do you have a sketch of how you will plumb it, including the direction you plan to install the check valves?

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