Bilge Pump questions

[Shanaro]

Hi all, I am going to install an automatic Bilge Pump in our 28 foot yacht. Please share your thoughts on what would be a sensible size pump to use. IE how many GPH would suit this size vessel? Is there a formula or basic rule of thumb to follow? I know some will likely say the bigger the better but the physical size of some of the extra large pumps could obviously be a drawback. Also your opinions on where the outlet should be located.

[boris]

Biggest is best as it gives you more time to sort a patch/repair

Unless you are just wanting to remove a little rain water from the bilge

[carstenb]

The bigger the better. But you noted automatic so you need to switch it off when you're not around, if rainwater or the like have ingress to the bilge. It will drain the batteries quickly if there is any water.

[Shanaro]

Thanks guys, my intention is to leave it on auto when not on board. The boat is often unattended for several weeks.

[carstenb]

Then you need to be sure there is no ingress of water (like rainwater). Otherwise the batteries will run flat.

On the other hand, if you end up with a hole in the boat (say hose pops off and ball valve is open) and you're not around for several weeks, the pump will not help you. It will pump until the batteries run dry, then the boat will sink.

[Hudson Force]

Originally Posted by Shanaro

.............. Also your opinions on where the outlet should be located.

Many choose to have the outlet well above the waterline. This would lessen the chance of water entering the effluent, but usually results in an ugly stain running down the freeboard. Many have the effluent in the boot stripe just an inch or two above the waterline, but at this location an anti-siphon loop is essential. Without the anti-siphon loop each time the vessel rocks it can take in a sip of water and this can add up quickly.

[Snowpetrel]

Ideally put the outlet up high and toward the center of the transom, No chance then of the thing siphoning back when you are heeled over hard. If there is any possibility that the outlet may be underwater when you are sailing hard don't put complete trust in siphon breakers or non return valves. Fit a valve somewhere in the system just in case.

[GordMay]

ABYC Standard H-22 (Electric Bilge Pump Systems) requires that Bilge Pump Discharges be located above the maximum heeled waterline; or have (both) a seacock and vented anti-siphon loop (not a check valve).

[mrohr]

Manuals always work if your arms are still all attached.I understand the argument for el pump when not aboard but one does not then readily know if any of the inevitable leaks are increasing/decreasing or if its rain water, plumbing, or sea water, melting ice water from leaky ice chest ,etc etc..If one really wants to know what is going on with their craft a manual pump is another way to take the pulse of your ship.
Easy for me to say since I have a smaller boat and have thereby developed bigger biceps along with greater understanding.

[Ex-Calif]

I have a 500 gph pump. You may consider 800 gph. It is wired to the house. The house is 140 a/h and topped up by solar.

You won't save a boat with batteries and a bilge pump from a catastrophic failure.

My outlet is pretty much as Gord describes.

[djmarchand]

A better setup is to have a smallish bilge pump mounted low and a larger one- 1000 gph or bigger, with its switch mounted a few inches higher than the smaller one.

David

[HopCar]

I vote with David on this. Install two pumps. One small and as low in the bilge as possible and one larger a few inches higher than the small pump. The problem with mounting large pumps in a small bilge is that the discharge hose can hold enough water to cause the big pump to cycle on and off endlessly. With luck the large pump will never come on.

[rtbates]

I caution against using the drop in centrifugal pumps unless your bilge is and will stay spotless. The impeller will jam on virtually anything. Hair, slivers of wood, piece of caulk, etc. and render it useless After having my Rule 1500 not function too many times, I switched to a remote mounted diaphragm pump. Mines a jabsco pump mounted in a cockpit locker. In the bilge is a strum box with built in one way valve and an electronic water detection switch. Five years and it's not needed to be touched.. It will suck up marbles and spit them out the transom. The outlet should be well above the waterline...

The system I described is NOT cheap, but then neither is my Cape Dory, haha..

[sarafina]

I like a couple of things that keep it working. Install the pump in a sieve that keeps the chunky stuff away. 1/4 inch hardware cloth works well. Big enough to allow the free flow of water , but fine enough to keep what would choke the pump from getting thru.

The idea, that I have not used yet but plan on, is installing a float switch higher by a bit than the pump and putting a float on it that reaches down to the pump level. In the past the switch has been the weakest link in the chain. This way it will be up out of anything that might muck it up.

[cal40john]

There's at least 2 different problems being addressed. One is a catastrophic hole, the other is maintenance.

Catastrophic, you want the biggest pump you can fit. One surveyor points out it takes a lot less water to sink a small boat than a big one. As others have pointed out if you're not at the boat or have an alarm that someone will do something about, a big pump won't do any good. A diaphragm pump isn't big enough for this use.

For small amounts of water a maintenance pump can be small. A diaphragm pump will pump air and water, potentially making for a dryer bilge and it has 2 check valves in it, less worries about backflow. If you go with centrifugal you want a small pump as all the water in the hose will drain back into the bilge, so smaller pump, smaller hose, less water remaining in bilge when pump turns off.

I also like the 2 pump idea, I have a diaphragm pump for my deck leaks and a big centrifugal mounted higher for sinking.

You want an hour meter on the pump to let you know if leaks are getting worse while you're away.

One argument against mounting the outlet as high as possible is pressure head is determined by the difference in height from the inlet to outlet. A centrifugal pump's output is affected by pressure head. It is not determined by the highest point of the hose.

How big is big
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