Stupid bilge pump design or...?

[Stephen Trapani]

Got to my boat a couple weekends ago and found the bilge pump wasn't working. Very long story short (the long story was about how long it took me to figure it out! I think the float switch went bad, failing to turn off when down), I discovered that when the battery bank is low the off-the-shelf Rule pump runs, pushing water out of the pump, but isn't strong enough to pump water all the way out of the above waterline discharge. So it will just run and run, pumping nothing until it completely drains the battery bank. When my solar panel manages to charge the bank a little, the pump will start up again, pumping no water out of the bilge, running until it drains the battery entirely.

Is this the way a bilge pump is supposed to work?

 

[woodster]

it will not pump with low voltage ...but will run just not fast enough to push water

 

[Stephen Trapani]

So..

This is normal for bilge pumps? I tried to put enough of a charge in the bank before I left, but I'm pretty much guaranteed that if the charge gets low enough the running but non-functional pump will serve to prevent the battery from ever charging from the solar panel. Isn't this kind of a dumb design? What am I missing?

 

[woodster]

This is normal for bilge pumps? I tried to put enough of a charge in the bank before I left, but I'm pretty much guaranteed that if the charge gets low enough the running but non-functional pump will serve to prevent the battery from ever charging from the solar panel. Isn't this kind of a dumb design? What am I missing?

your float switch turns the pump on and off if it is defective it will not spits job. Check and make sure it working properly if not you may have to replace the the switch

 

[woodster]

Do its job .....dang iPhone won't let me edit

 

[uncledom]

I use a check valve in my bilge line not far after the pump. More than one boat I have owned has had a problem with pumping water up the hose and having it drain back down till there was enough in the bilge to re-engage the float and pump. That is to say that once the float is satisfied and shuts off the pump, the amount of water in the exit hose is enough to run back down and fill the bilge enough to engage the float and turn the pump back on. This will happen until you drain the battery. Put a check valve in two feet away from the pump. Very little water will drain back to the bilge upon shut off. Make sure you run antifreeze through the pump during winterizing.

 

[kloudie1]

Centrifugal pumps need to turn fast enough to generate enough pressure to push the water out. When the battery gets low, or if there is a bad connection or corroded wire in the circuit, there won't be enough electricity getting to the motor to make it spin fast enough. If you have no other charge capability, it may be prudent to get a portable generator and fully top off the batteries once you've fixed the switch.

 

[Daveinet]

http://www.waytekwire.com/item/80029/SURE-POWER-130512-LOW-VOLTAGE/
or just search for low battery cut off.

 

[Stephen Trapani]

Why no cutoff built in?

Thanks for the answers guys. FWIW, I did replace the float switch and pump (twice!) before I figured out what was going on (I'll leave out the dark, rain, 4 paddle outs, climbs up the stairs, and drives to the store). I just couldn't believe that my solar panel would never be able to charge a low battery bank due to this design of pump, and that this was common. I guess it is.

The low battery cut off should solve it and looking at it's price, I guess that's why it's not a standard feature of bilge pumps. Don't know why I haven't run across this problem before, or why it doesn't cause a lot more problems for people.

 

[All U Get]

Re: Why no cutoff built in?

Thought about your problem and maybe a small pump with very small diameter hose sitting in the deepest part of the bilge would work better. When it cycles there would be less volume remaining in the line so when it drains back it wouldn't trip the float again. Of course you would still want a large one to remove big volumes.

All U Get

 

[centerline]

Thanks for the answers guys. FWIW, I did replace the float switch and pump (twice!) before I figured out what was going on (I'll leave out the dark, rain, 4 paddle outs, climbs up the stairs, and drives to the store). I just couldn't believe that my solar panel would never be able to charge a low battery bank due to this design of pump, and that this was common. I guess it is.

The low battery cut off should solve it and looking at it's price, I guess that's why it's not a standard feature of bilge pumps. Don't know why I haven't run across this problem before, or why it doesn't cause a lot more problems for people.

You never did mention the size of the solar panel.... but if the power draw of the pump is more than what the panel can put into the battery, its obvious that you will have a problem if the float switch sticks on.

And depending on your solar set up, the weather, and the amount of discharge in the battery, it could take up to a month to charge the battery to an acceptable level

 

[Stephen Trapani]

The float switch is fixed and the water draining back from the hose is not retriggering the switch. These are not the problem now. The switch turns on the pump when there is enough water in the bilge and if there is not enough charge in the battery, the pump will run and run until it completely drains the battery without pumping out any water, leaving the float switch up. When my 50w solar panel charges the battery enough, the pump will presumably run again (since there is still water in the bilge holding up the float switch), but without enough charge in the battery it will just run the pump until it drains the battery completely. This will go on forever, right? until someone puts a lot more charge in that battery bank.

See my point? The solar panel, no matter how big it is, will turn on the weak functioning pump just enough to drain the battery indefinitely and not enough to pump out any water!

 

[Stephen Trapani]

BTW, the way I have this figured at the moment, this isn't just my problem, it's the problem of every boat owner who doesn't have a low battery cutoff. Once your battery charge gets low enough it will cause your bilge pump to run (once the float switch turns on) without pumping out water. This will keep your battery drained indefinitely even if you have any kind of slow charger on it like a solar panel. What am I missing?

 

[Ron20324]

..., it's the problem of every boat owner who doesn't have a low battery cutoff.... This will keep your battery drained indefinitely even if you have any kind of slow charger on it like a solar panel. What am I missing?

You're missing the point of why not drain your battery down to zilch? Why keep ANY charge in the battery if it does not run the pump? If the battery dies, that means the pump don't pump, and the boat will flood and sink eventually. So what's the cost of a battery compared to a sunken boat? If the boat sinks and has a battery cutoff, what are you gonna do- listen to the stereo when the boat is sitting on the bottom?

 

[Stephen Trapani]

I get what you're saying Ron (I think!), but if a person is leaving their boat for months at a time sometimes, with a solar charger, a low battery cutoff would allow the battery to charge enough to pump out the water before it turns on the pump, wouldn't it? As it is now once it gets low the battery will never charge because the pump will always run without pumping out water.

 

[Charles Erwin]

Stephen

What you are describing is probably an hysteresis (repeated cycling) due to discharge hose contents flowing back to the sump and reengaging the switch.

Otherwise the float switch itself is bogus. After experiencing events identical to yours I changed to a different switch

https://www.waterwitchinc.com/online_cart/index.php

This completely solved the problem. Constant running on or repeated cycling was eliminated which means the battery will have plenty of time time to recover.


Charles

 

[Stephen Trapani]

Stephen

What you are describing is hysteresis (repeated cycling) due to discharge hose contents flowing back to the sump and reengaging the switch.

Consider this approach: https://www.waterwitchinc.com/online_cart/index.php

Charles

Hey Charles! I don't think that's the problem. When my battery is low and the float switch is up the pump will run and run and run without pumping out ANY water from the bilge. This is what I'm asking about.

 

[Charles Erwin]

But you have been on a float for a good long time. Is this a recent problem or has it been something you have always lived with?

I expect you have ruled out leaks in the discharge hose/fittings and also that the pump is up to it including that the impeller/strainer are spiffy clean.

Charles

 

[kloudie1]

So the only way to really protect against the failure of the float switch is, as you've noted, to put in a low volts shut-down.. but ya have to be able to adjust it somehow so that it shuts down at a smidge over 12 V but does not turn back on until it hits around 14 V.. or put in a big honking panel with a capacity of over 100 Watts.
What is the watt rating of your panel?

 

[Benny17441]

If leaving the boat unattended for a long period of time, shut off the bilge pump. The small electric bilge pumps will not prevent any major water intrusion but as you have experienced may lead to draining and eventually killing your batteries. The bilge pump was designed to remove from the boat incidental water that collects in the bilge and not to prevent a boat from sinking. The best prevention is to identify the sources of water intrusion and promptly correct them. It will take years to sink a boat from small leaks. Also remember it is the smallest boats that are more susceptible to leaks as they have the less volume of hull interior.