Bilge pump that leaves very little water available?

jarcher · #1 (**permalink**) 06-21-2010

Hi All...

I have been searching, including here, but no joy yet. I would like to get lots more water out of my bilge. The pumps I see seem to leave at least half an inch, but usually more, plus the thickness of the board they want you to mount it on, in the bilge. So that means there is going to be an inch and a half of water, or more depending upon the switch used.

Does anyone make something like the pumps we pump out our basements with? Those pumps sit on the floor and have like a 1/4 inch opening at the bottom, and suck up water leaving virtually none.

Thanks...

Jim

sailingdog · #2 (**permalink**) 06-21-2010

The issue is that most bilge pumps will back flush when the pump shuts off. This means that you'll get a bit of water remaining in the bilge. The easiest way to minimize this is to use the smallest bilge pump as you can for your "maintenance" pump with the smallest hose diameter that you can use. This will minimize how much water can back flush.

Another option is to use a separate float switch and a much more expensive diaphragm type bilge pump, which won't back flush, since a diaphragm pump basically has two check valves in it. Put the float switch and strum box for the bilge pump intake hose in the lowest spot in your boat.

eolon · #3 (**permalink**) 06-21-2010

I have had good luck with the Rule auto bilge pump 500 - it is Rule's smallest and will get all but a small puddle out of the bilge. THe pump is a float-less type which turns on automatically every 2 1/2 minutes or so. If there is no load on the pump (no water in bilge) it shuts off. The current draw is tiny - my solar panels easily make it up. I have a check valve in the small (1/2") hose out of the pump that prevents backflow. The discharge must be above the waterline, of course, including the waterline when heeled.

Check valves have a reputation for failing, so I have 2 larger back up bilge pumps on floats in case the little one fails or can't keep up with a serious leak. I also always have one or two buckets on board.

Best Regards,

e
.::.

jarcher · #4 (**permalink**) 06-21-2010

Thanks everyone. I have a Rule fully automatic 800 GPH that I am looking to replace. I like the automatic aspect of it. The first one I bought didn't work and the vendor replaced it. That was last season and it works all summer.

This year the boat came out of storage and the automatic part was not working. I can turn it on manually and it pumps, but the evert 2.5 minute part is dead. Rule is sending a replacement under warrenty. It takes 3 weeks!

But this pump still leaves well over an inch of water because it needs at least half an inch before it can suck the water out. I can handle a switch, but I'm looking for a pump that works with a very low level of water.

If I understand SD correctly, he feels the issue is that the water comes back in from the hose, and it does. But still, the pump needs a certain level before it can move water to begin with.

CLucas · #5 (**permalink**) 06-21-2010

Check out the Whale Supersub 500 -- you can't eliminate the backflow issue, but this pump has a very low profile design which is supposed to yield better results.

jarcher · #6 (**permalink**) 06-21-2010

I did, thanks. No where does Whale document how much water is needed to make it work properly. It looks pretty low though. They also have a fully automatic version.

CLucas · #7 (**permalink**) 06-21-2010

Quote:

Originally Posted by jarcher

I did, thanks. No where does Whale document how much water is needed to make it work properly. It looks pretty low though. They also have a fully automatic version.

Whale actually recommends a one-way backflow-prevention valve, which as you pointed out, are susceptible to failure. Unless you're talking about the fully automatic version, I would think that the amount of water to make it work properly would be dependent on the float switch and not the pump -- right? If it's the float switch, I wonder if it could be modified to reduce the distance the float needs to travel to close the circuit. Just a thought.

jarcher · #8 (**permalink**) 06-21-2010

Good point with the float switch, but my bigger concern is that with a pump, the water level has to be completely above the strainer, or it sucks up air. The Rule and other pumps have a strainer thats like half an inch tall or taller, then you have to mount it on a block of wood...

I guess its really not that important. I'm just trying to keep things dry.

eolon · #9 (**permalink**) 06-21-2010

I took the strainer off, and mounted the Rule on an aluminum angle that keeps it in contact with the bottom on the bilge. The bilge is very dry - the little water that the pump leaves usually evaporates in a day or so.

Also, I mounted the check valve very close to the pump discharge - so very little backflow.

With no strainer on the pump, you have to keep big chunks out of the bilge, though...

Best Regards,

e

.::.

bluwateronly · #10 (**permalink**) 06-21-2010

I think you are over-thinking this. SD suggested a small pump to get the 1 inch or so left and I think that is a good idea. Why spend the money for a main bildge pump when you can install a smaller and your main will be there when you need it? Oh,, forget the check valve, keep this part of your system as simple as possible.