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Old 01-01-2020, 08:56   #1
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Low-Level Sump Pump

I sail a number of boats with very shallow bilges (not the cat in the avitar). At 1 1/2 inches there is water on the cabin floor. Obviously, the common float switch range and bilge pump set-up is less than satisfactory (on at 2 inches, off at 3/4 inches).

ABYC has standards for sump pumps on recreational craft. They do not require a UL listing, but the pump does need to meet a variety of requirements.
  • Ignition protected (but not NEMA explosion proof).
  • Run dry period without excessive case heating.
  • Numerous installation requirements.
  • Screening is a common sense requirement.
The smaller the pump is, the easier it is to meet the second requirement. Some only pull an amp at full load and less MT. It's hard for 12w to get hot. No, a tiny pump won't move much, but you can always back it up with something conventional and large.



(A small pump, like this, can easily work in the 1/2-1" range. Still not dry, but below the floor.)



Pumps can be run on timers with very short intervals. The auto pumps work on this principle. Not the best thing for seals, but they probably aren't dry and there is little heating potential in smaller sizes. No float switch.

I'm aware of the Arid Bilge System. Basically a tiny, automated, reversible Shop Vac.


Anyone rig something up for very shallow bilges?
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Old 01-01-2020, 09:18   #2
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Re: Low-Level Sump Pump

I’m trying to imagine a bilge with a depth of only one and a half inches.
You meant inches, not feet?
Even the smaller run abouts and ski boats, Center Consoles I’ve had had bilges of at least I’d say at least 6” deep, and those were boats where water wouldn’t hurt anything.

A couple of inches is no bilge, what boat has no bilge?
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Old 01-01-2020, 10:03   #3
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Re: Low-Level Sump Pump

Quote:
Originally Posted by a64pilot View Post
I’m trying to imagine a bilge with a depth of only one and a half inches.
You meant inches, not feet?
Even the smaller run abouts and ski boats, Center Consoles I’ve had had bilges of at least I’d say at least 6” deep, and those were boats where water wouldn’t hurt anything.

A couple of inches is no bilge, what boat has no bilge?

Corsair F-24. Measured it. Also numerous other centerboard performance boats. The bottoms are flat for planing. Basically, the cabin liner lies on the flat bottom, with a groove down the middle to allow water to a central low (?) point.






There are about 1.2 inches between the hull and the bottom of the hull liner in the groove down the center, and less than 1/2" outside of the groove. By the time you are 10 inches off the centerline, there is no bilge.


It's a trimaran, so sinking is a non-issue and generally they do not have bilge pumps. Generally it stays dry. But there are exceptions, including weeks of rain and very heavy sailing.
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Old 01-01-2020, 10:31   #4
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Re: Low-Level Sump Pump

I think I would fit a small diaphragm pump with the pump somewhere it can easily be accessed, a diaphragm pump mostly because they self prime and do not have to be in the water. But I would want it accessible to clean out its strainer and work on the pump of course, but if a bilge is only an inch and a half deep, then it’s going to be tough to fit a pump in there? So remote mount it.
I’d then run it with a manual switch, or if I wanted to get fancy find a switch that senses water by conductivity, like the water alarm’s do, all it takes is a tiny bit of water to wet their contacts and they alarm.
But I think a manual switch would be OK, a diaphragm pump can suck something almost completely dry, just not a whole lot of volume.

I have one mounted in my engine room to pump out my shower sump, that my icebox and air conditioners also drain into, it’s triggered by a float switch though as I strongly suspect my shower sump is just a kitchen sized good trash can. Al least it bears a strong resemblance to one.

Maybe put a battery powered basement water alarm in the bilge to tell me when there is water so I would know to switch the pump on, they are inexpensive and really work well
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Old 01-01-2020, 19:12   #5
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Re: Low-Level Sump Pump

Yes, that could work.
* Diaphragm pumps don't always self prime if dry.
* Overkill. But logical.

* An alarm is good, but not helpful if I'm not there, which is when it matters. It's those times when I am away for weeks of heavy rain.
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Old 01-01-2020, 20:28   #6
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Re: Low-Level Sump Pump

A diaphragm pump won’t be hurt if dry run either, so a timer may be one way if you just can’t make a float switch work.

This little guy will reliably self prime with water 4’ below it, and do so every time. Mine has for the five years I’ve had it anyway, and supposedly dry running one doesn’t hurt it as it has no shaft seal etc. it just flexes a diaphragm.
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Old 03-01-2020, 07:01   #7
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Re: Low-Level Sump Pump

What are the dimensions of that pump you are using? Is it sitting on a bracket? I can't really understand from the camera angle, but can tell you have little room to work in!


Is the float switch the problem? Can you tilt the mounting so that it will cut on sooner?


Not the perfect solution, but I will suck the last bit of water out with a pool toy/squirt gun.
https://www.amazon.com/Boley-Super-W...&sr=8-101&th=1


I have bought them single or in 4 packs from Walmart
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