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Old 08-05-2011
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Bilge pump failure(s)

Hello-

Im new to this site. I recently purchased a Contessa 26 (supposedly a 1985 but this is a topic for another posting). My question is in regards to best bilge pump. The bilge is very deep, probably 3 feet deeper than cabin sole and there is quite a long run to the current thru-hull. I intially tried a jabsco diaphragm pump which failed on the 3rd or so use, Then I tried a rule 1200 which doesnt seem to have the power to pump this distance. I have spent some dollars on different tubing etc and am at my wits end! In Jabsco's defense they sent me a new pump no questions asked.....

My questions are:
a) what is the best pump for deep keel bilge boats and a run of 8 feet or so horizontal and vertical run of roughly 6-7 ft.
b) if i use a diaphragm pump is it more efficient to mount higher such as in cockpit lazarette (longer suction run, shorter output run to throughull) or is it more efficient to mount near bilge (short intake run, long output uphill) or does this not matter at all.
c) what is the best tubing diamater. The jabsco pump calls for 3/4 inch. If I use the new jabsco pump should I step down to smaller diameter due to long output run?

Any suggestions from anyone with deep keel bilges would be greatly appreciated. I am done trying to brush up on my physics/fluid dynamics.

Many thanks
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Old 08-05-2011
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Quote:
Originally Posted by ebrown76 View Post
Hello-

Im new to this site. I recently purchased a Contessa 26 (supposedly a 1985 but this is a topic for another posting). My question is in regards to best bilge pump. The bilge is very deep, probably 3 feet deeper than cabin sole and there is quite a long run to the current thru-hull. I intially tried a jabsco diaphragm pump which failed on the 3rd or so use, Then I tried a rule 1200 which doesnt seem to have the power to pump this distance. I have spent some dollars on different tubing etc and am at my wits end! In Jabsco's defense they sent me a new pump no questions asked.....

My questions are:
a) what is the best pump for deep keel bilge boats and a run of 8 feet or so horizontal and vertical run of roughly 6-7 ft.
b) if i use a diaphragm pump is it more efficient to mount higher such as in cockpit lazarette (longer suction run, shorter output run to throughull) or is it more efficient to mount near bilge (short intake run, long output uphill) or does this not matter at all.
c) what is the best tubing diamaeter. The jabsco pump calls for 3/4 inch. If I use the new jabsco pump should I step down to smaller diameter due to long output run?

Any suggestions from anyone with deep keel bilges would be greatly appreciated. I am done trying to brush up on my physics/fluid dynamics.

Many thanks
Your problem is probably the "head" height. Bilge pumps don't like lifting water great heights. Also, the pump should be down in the bilge - no input length. You have probably noticed that many, if not most, electric pumps have the pickup on the underside of the body and they sit IN the water in the bilge.

Electric pumps are generally designed to push, not pull - that's why modern cars have their fuel pump in or near the fuel tank.

I'd also advise lowering the output level - put a through hull near the water line to lower the head height. The length of the output hose is not as much of a problem but it should be as short as possible for best performance.
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Old 08-05-2011
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My primary is also a Jabsco diaphragm pump. I don't have a model number handy, but recall it pumps 750gph. I would say the intake is approx 2 feet below the pump and the through hull is 25 feet away and another 2 feet higher. Both estimated, never has trouble pumping/pulling.

I also have an in-water 1000gph Rule backup pump.

Both have separate float switches, the backup switch being higher than the primary.

Best efficiency move one can typically make is to get bilge line that is smooth inside.
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Old 08-05-2011
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Go to your hardware store and purchase a 12 back up sump pump
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Old 08-05-2011
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I disagree with SloopJonB

The outlet should not be too close to the waterline or there is a serious risk of water finding its way in instead of out. The outlet can be about halfway between the waterline and deck but the hose should loop up to the deck and have an anti-siphon valve fitted at the top of the loop prevent this.

If the pump you choose has a 3/4" outlet the hose should match it - if you make it smaller you are restricting the flow and making the pump work harder. There is also no advantage in making the hose larger.

Use hose that is smooth inside as a internally ribbed hose will also restrict flow.
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Old 08-06-2011
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No problem at all with a bilge pump outlet near the waterline, so long as you have an anti-siphon loop and, preferably, a seacock you can close when sailing/heeling.

I concur with Brian re: hose size. Don't ever go smaller than the pump outlet.

Best pump I've found -- and I've tried them all over the past 28 years -- is the FloJet (NOT the ShureFlo). ITT bought these a few years ago, and so far they haven't fooled with the design...only the price!

I won't have any other pump aboard. Flojet pumps for bilge and pressure fresh water systems. They handle the lift you have just fine. I have three which are mounted just under the cabin sole and have pickups extending down some 5' into the bottom of the bilge.

The main problem you have to solve, eventually, is with the bilge pump float switches. These are notoriously unreliable. Again, I've tried them all and they're all crap...except for, of course, the quite expensive ones. After dicking around all these years, a couple of years ago I bit the bullet and went with the UltraSwitch Senior and UltraSwitch Junior for my two bilge pumps, with a high-water alarm as well. $300 investment, but well worth it. No more problems.

Short of that, I found the much less expensive electronic switches (have two metal contacts and work by sensing water between the contacts..no moving parts) worked reasonably well for several years, providing you keep the contacts clean and don't have an oily bilge.

Avoid the float switches with the moving arm like the plague. They're all -- and I'm going to use a technical industry term -- CRAP!

FWIW,

Bill

Last edited by btrayfors; 08-06-2011 at 09:10 AM.
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Old 09-06-2011
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A few comments

1. Placing the bilge water outlet nearer the water line but adding in the anti-siphon loop really does nothing to reduce the head the pump must overcome.

2. Some advise a small capacity pump as the first line of defense to deal with nuisance level of bilge water, with a 3/4 inch outlet then reducing to a 1/2 line. This reduces the volume carried in the hose (and that returns to the bilge when the pump switches off).

3. There are differences between diaphragm pumps and centrifugal designs. The former can be placed above the bilge water and will pull it up and then push it the remainder of the run to the outlet. These are generally more expensive and have more working parts, but also can be rebuilt. Centrifigul pumps sit in the water and push it the entire run of hose to the outlet. They are cheaper but throw-away (tho some allow replacing the pump cartridge in the old case; a small savings over a new pump.

4. Smooth-walled hose is a must

5. Any functional bilge pump should be able to overcome your 6-7 vertical feet of head... but, the rate-of-flow will be greatly reduced from the pump's rating... like half the flow.
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Old 09-06-2011
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GRTEETINGS EARTHLING ; Whynot fit a none retrun valve to the main pump just after the strum box (filtter thing in the blidge) Go SAFE
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Old 09-08-2011
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A check valve is OK to prevent water still in the hose from draining back into the bilge when the pump cycles off. A check valve is not a replacement for a high anti-siphon loop because check valves can and do get stuck open.

In the first use case with a stuck check valve, a little water drains back to the bilge. In the second with no anti-siphon loop, a stuck check valve can mean big big trouble.
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Old 09-08-2011
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Quote:
Originally Posted by hriehl1 View Post
In the first use case with a stuck check valve, a little water drains back to the bilge.
Careful there --

Depending on your installation (bilge geometry, switch location, plumbing run,etc.), this could also mean a constantly cycling bilge pump -- pump pushes water up into the hose to the a/s valve; pump shuts off; water drains back into bilge causing float switch to activate; repeat until either a) main switch is turned off, or b) batteries die.
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