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Bilge pump failure(s)

4K views 12 replies 11 participants last post by  sfchallenger 
#1 ·
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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#2 ·
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.
 
#3 ·
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.
 
#5 ·
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.
 
#6 · (Edited)
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
 
#7 ·
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.
 
#9 ·
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.
 
#10 ·
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.
 
#11 · (Edited)
You are correct... which is why I reduce the line from 3/4" ID to 1/2". That holds, and returns when the pump cycles off, about half the water a 3/4" ID hose does. Yes, it also restricts flow-rate, but my little first-line-of-defense pump only clears nuisance amounts. I have a second hi-capacity pump for emergency back-up if ever needed.

But you are right, with no check valve (even with one, they do stick open) one must make certain that backflow from the hose run would not re-start the pump.
 
#12 ·
I do pumps, like every day. Centrifugal pumps operate on a pump curve. The left top end of the curve is the shutoff point, maximum pressure @ no flow. The curve slopes downwards towards greater flow and lesser pressure. For any given pump the pressure vs flow it will always fall on the curve, and thus is completely predictable. Practical Sailor did bilge pump tests, I took them to task for not including a curve for every pump.

There are two kinds of head against a pump, lift head, and friction head. There isn't a lot you can usually do about lift head, you need to get the water up there. But friction head comes from rough interior hose surfaces, friction against the walls x hose length, and friction from valves, enlargements, and restrictions. Always keep all hoses as short as possible, and as LARGE as possible. If your pump has a 3/4" Outlet and the run is long, say 10 feet or more, increasing the hose size to 1" or 1-1/4" will make a big difference.

I was just in California on a trouble call. We like the back pressure on a filter permeate line to an absolute minimum, like 0 to 1 Psi. The job had 160 feet of pipe, 5 elbows, 5 valves, and 5 tees! Yeah, that's gonna work.
 
#13 ·
A lot of good info here, I'll toss my hat in the ring as well:

I like Johnson pumps, they seem fairly reliable (I haven't had such good luck with Rule, but may seem to like them as well) and also like redundancy. I'd pick the largest pump that will fit in your bilge as a primary, for my boat that is a 2200 GPH with a 1 1/8th output. A secondary (and tertiary) pump is a great idea, but it can't be plumbed through a Y to the same through-hull or you risk the constant cycling. A check valve might be used for this purpose, but as others have noted here, they get stuck and cannot be relied upon.

One important thing to remember is that during an emergency, when you are taking on a lot of water, all the loose crap in your bilge will go straight to the pump. For this reason I'm not a huge fan of diaphram types - during an incident on my boat involving a badly leaking packing gland both debris strainers for both diaphram pumps on board became clogged immedietly and both pumps lost much efficacy. Doesn't sound hard to fix, but when your attention is occupied by the water coming *in* to your boat you won't have time to troubleshoot the pumps. Since that incident I keep a 'backup to the backup' pump in a locker, with long leads soldered on and enough hose attached to get from the bilge to the cockpit. The idea being that even if my electrics are fried I can quickly hotwire the pump to the battery and run a hose overboard. Of course, I have a manual in the cockpit too,

Cheers,
h
 
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