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post #1 of 24 Old 01-29-2007 Thread Starter
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Bilge Pumps

My boat has one bilge pump that is operated from the cockpit, just aft of where the helmsman would sit. It is a manual Whale Gusher 8. I want to add an electric with float switch. How do I go about sizing a bilge pump? My boat is a Pearson 28. Also, is it wise for it to be plumbed to use the same through hull fitting as the manual pump?
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post #2 of 24 Old 01-29-2007
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For size, go with the largest that will fit in the space you have for it. I would plumb it to a new thru-hull though. That way, heaven forbid, if you need to use both at once, you can.

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post #3 of 24 Old 01-29-2007
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If starting from scratch, I would install 2 electric pumps. For the first I would get a small pump with the smallest diameter hose fitting available. I would install this pump in the bottom of the bilge. This first pump will run anytime you get water in the bilge and with the small diameter hose you will get less backflow into the bilge when pump shuts-off and keep your bilge drier.

I would then install the largest pump that will fit, as PB suggested, on a stand or platform about mid way down into the bilge. This second pump will be available to do the true heavy lifting in case of major water intrusion. This is a method that has been suggested by a number of different authors, in a few publications. Seems to represent the best possible solution.

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post #4 of 24 Old 01-29-2007
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I'd second T34C's suggestion... since many boats have small, annoying leaks, and those need to be dealt with on a periodic basis... and then a larger, high volume one for emergencies.

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post #5 of 24 Old 01-29-2007
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You can use the same thru-hull but will need to install line check valves to each discharge line prior to their becoming common discharge. With two electric pumps plumbed this way they would tend to fight each other, with one or the other doing the only work, but with your manual, positive displacement, pump you will not have that problem.
34's idea is the best way to cover all contingencies. I have seen "portable" pumps made up with a small dc pump mounted to a broom handle or such, with the discharge hose running up along the handle, and the electric cord extra long with alligator clips. This allows one to move about, from compartment to compartment, with the pump and not be constrained by discharge plumbing and "hard" electrical wiring.

A strainer box around the base of the pump is not a bad idea, but can probably be omitted if the pump location is readily accessible. "Readily accessible" is usually not the low point in your bilge, unfortunately. It does not hurt to think about having to remove the pump, to clean the suction screen, while having a foot or more of dirty water over it-in the dark! A pump location that may not pump your bilge completely dry, but is easily accessed, may be of more importance when that bad day arrives where you've really got to move some water. Which I guess brings us back to where 34 came in.
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post #6 of 24 Old 01-29-2007
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Check valves in bilge pump lines are generally a really bad idea. They add a fair amount of back-pressure to the output lines of the pumps and greatly decrease the output volume.

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post #7 of 24 Old 01-30-2007
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Speaking of which, my thru hulls are below water line and every wave splashes back into the hose draining into the bilge. I have the hose pinned up as high as it can go. Im wondering if there is a check valve or better yet a "trap" I can put in there? Never had this problem so bad before. I wonder if a loop in the line would work?
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post #8 of 24 Old 01-30-2007
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The best system on my opinion is – Pump that does not stay in the water / beneteau comes with such factory installed / pick up hose with strainer at the end in the lowest part of the bilge. Warning light and sound alarm connected to the pump. Pump hot wired to the house battery with switch ON - AUTO / never off / , fuse appropriate size. Wiring / connections / should be done with heat shrinking isolation and anti corrosion grease.
Thru-hull at transom above the water line, hose with loop / you can see it when water starts coming out / specifically designated only for this pump and NO check valves. Float switch should have exposed floating part / you can check system operation every time you are on board by lifting the float with your finger. Keep the area around the float free of items that can collapse on top of float. Keep your bilges clean of debris. Buy BIG bilge pump, the smaller the boat the faster will sink from same size hole at the bottom.
Good luck


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post #9 of 24 Old 01-30-2007
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A properly sized check valve should provide minimal back pressure and little reduction in volume. Aside from the obvious ability of keeping the water moving in one direction they will also protect centrifugal pumps from extraordinaryly high head pressure as well as back-spinning of the impeller at shut-down, the latter being a major cause of premature pump failure. Spring check valves are much more reliable and flexible in usage. I would not recommend a swing check valve. Your hand bilge pump is actually just a couple of checks valves.
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post #10 of 24 Old 01-30-2007
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So my loop idea is valid? I guess I have never seen or needed to look for a check valve. This is another first. Who the heck would put thru hulls UW? Discharge ones anyway. I like to see when my pump is running.
Another question, who makes a pump that stays dry? That is the pump is not in the water.....
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