Bilges - On vs. Automatic; Capacity? - SailNet Community
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post #1 of 24 Old 01-19-2013 Thread Starter
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Bilges - On vs. Automatic; Capacity?

I have two bilge pumps in the center of my boat (from the original owner) controlled by two switches in my galley. One runs immediately when switched on. The other is a float-switch type that is meant to be left switched on.

- Why not just install two pumps with a float switch?

- Is there a reason not to get the highest GPH that you can find? I've seen 4000+ GPH. Why not put two 4000 GPH side by side both with float switches?

- The bilge pumps always seem to leave about an inch of stinkwater unpumped? Is that just because the filters need to be cleaned? Or is that typical?

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post #2 of 24 Old 01-19-2013
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Re: Bilges - On vs. Automatic; Capacity?

There is usually water in the discharge hose which runs back down into the bilge after the float switch turns the pump off... depending on how long the hose is and how it is run. Running the pump on the manual switch may get this lower, but it's virtually impossible to get everything out (though I've done it with a Shop-Vac in an otherwise dry boat).

Having a second pump is not a bad idea. One approach would be to install a float switch on the second pump but locate it higher than the first, so that one pump would take care of "normal" seepage (wherever it comes from) and the second would kick in if there was more water than normal or the first pump/switch failed.

I've often thought of doing this on my boat (where the primary factory pump is, unfortunately, a "shower sump" pump), but the problem is drilling out the ribs to run that second discharge hose.

Hope this sort of answers your question.
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post #3 of 24 Old 01-19-2013
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Re: Bilges - On vs. Automatic; Capacity?

David,

Easy question first: If you've got a centrifugal pump (like a Rule), then yes, it is quite typical for the bilge to never get completely emptied. What happens is that all the water in the discharge hose from the pump up to your anti-siphon loop will drain back into the boat when the pump is turned or cycles off. Some people install check-valves in the hose run to keep this backflow from happening -- please don't do it! There have been many threads discussion this here on SN; do a search and read on.

Getting a little more complicated, now...

A common set up for multiple pumps is for one high capacity pump on a float switch, paired with a small capacity pump that has either a manual or dual ("manual" & "auto") switch. The reason is that the smaller pump will typically have a much smaller hose bore (like 3/4") as opposed to a high capacity pump (which will normally have a 1-1/8" to 1-1/2" hose.) The smaller hose will hold less water in the run up to the anti-siphon loop, and thus you'll have less water flowing back into the bilge when the pump stops.

If you go elect to go this route, make sure you mount the float switch for the larger pump higher in your bilge than the backflow water level from the first pump.

As far as switches go, I actually prefer to have dual function switches; if your float switch fails, you can always bypass it at the selector switch by simply flipping it from auto to manual.
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post #4 of 24 Old 01-19-2013
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Re: Bilges - On vs. Automatic; Capacity?

One theory is that automatic pumps can actually sink a boat.
Let's say you have a stuffing box that starts to leak.
You don't notice and your automatic pump takes care of it for you.
This goes on for months and gets worse and worse.
You might notice that the battery seems a little down for one evening sail but don't think much of it.

You go away for a weekend. The leak gets much worse.
The pump goes on and stays on. The battery goes dead.
The boat sinks.

Some people solve this problem with a cycle counter others by having the lowest pump manual.
So every time you board the boat you know how much water it is taking on.
If it changes you know you have to investigate.

Just a thought, lots of people have fully automatic pumps and like it that way.
Everyone worries about different things.
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post #5 of 24 Old 01-20-2013
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Re: Bilges - On vs. Automatic; Capacity?

Two pumps, one higher than the other, both on auto. Another float switch connected to a LOUD alarm that will trip before the second pump activates. Alarm should sound in cockpit too. Gets your attention while sailing and your neighbor's while you're away.


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post #6 of 24 Old 01-20-2013
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Re: Bilges - On vs. Automatic; Capacity?

I have a two pumps

One low that does all the work on battery A

One high that never gets wet on battery B

One good size solar panel so nothing goes dead

It still did NOT STOP the boat next door from putting there bow sprite through the cabin top SO you can only worry about so many things and just try and keep the systems in good shape

When i take my boat sailing i can here the pumps if they go on and it takes 2 minutes a week to check the oil and give any leaks and eyeball
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Last edited by tommays; 01-20-2013 at 06:40 PM.
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post #7 of 24 Old 01-20-2013
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Re: Bilges - On vs. Automatic; Capacity?

Quote:
Originally Posted by davidpm View Post
One theory is that automatic pumps can actually sink a boat...
True Story.

Water Witch Bilge Alarm

When mounted in the cockpit, it's loud enough to be heard down below when sleeping, or by marina neighbors at your slip. The best $75 bucks I've ever spent on the boat.
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post #8 of 24 Old 01-20-2013
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Re: Bilges - On vs. Automatic; Capacity?

I have two pumps. One is a typical marine bilge pump with a float switch. It is on it's own electrical buss which i can leave on with the batteries in off to other house loads. The other is a basic (an inexpensive) Sears AC sump pump with it's own float switch (above the DC pump's) that runs direct from AC shore power. I figure that the latter gives me a very high capacity back-up which will run if my DC system some how fails). You can get a counter that tells you total bilge pump run time to track the problem of a chronic leak.
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post #9 of 24 Old 01-21-2013
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Re: Bilges - On vs. Automatic; Capacity?

My main bilge pump was wired to run automatically without going through my panel. It was also wired to be manually controlled. I'd recommend this arrangement, rather than just setting it up to only only automatically.

Why? Because your automatic switch might fail. I had a brand new Jabsco pneumatic switch fail the first time it was called to duty during a freak event associated with a 3 day-long Northeaster. It didn't sink the boat, but it did float my floorboards before I went to check on the boat. What if it were a more serious situation? Assuming you were on scene, you'd want to have another option to turn the bilge pump on. I do have a manual pump installed but that is only for extreme backup.

BTW, I never got a response from Jabsco on a warranty claim, not that would I trust their Chinese-made switch again. I replaced it with a Johnson Ultima switch that can be easily tested.
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post #10 of 24 Old 01-21-2013
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Re: Bilges - On vs. Automatic; Capacity?

A slow leak will first empty the battery via your lower bilge pump, and leave no power or alarm or second pump.

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Originally Posted by Minnewaska View Post
Two pumps, one higher than the other, both on auto. Another float switch connected to a LOUD alarm that will trip before the second pump activates. Alarm should sound in cockpit too. Gets your attention while sailing and your neighbor's while you're away.
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