Bilge pump cavitation

Shortman · #1 (**permalink**) 05-05-2008

I have a standard Rule 1000 GPH submersible bilge pump that works fine but, sometimes after some good heeling will catch an air bubble in the inlet and get air bound & run & run. Anyone run into this? Have a fix? Know a different brand that does not get air bound?
It looks like setting the switch higher might do the trick, but I would prefer to stay drier.

Zanshin · #2 (**permalink**) 05-05-2008

I thought that the bilge pumps were all self-priming; so even after sucking air they should still be able to lift water. My 2nd bilge pump is a rule as well and it certainly has no problem mixing air / water

sailaway21 · #3 (**permalink**) 05-05-2008

I'd expect you have either a plugged impeller or a restriction in discharge. either one could cause your symptom accompanied by a loss in pumping efficiency at greater bilge water depth. You might also have a worn impeller which would probably necessitate replacing the pump, although I've never had one apart. If you find the impeller blocked just run some wire through the vanes into the eye-you will hopefully will not even need to remove the impeller to do this. Good luck and let us know how you come out.

bubb2 · #4 (**permalink**) 05-05-2008

Put a check vale in the discharge the pump is trying to pump the same water over and over

sailingdog · #5 (**permalink**) 05-05-2008

Check valves aren't very good in bilge pump lines since they drastically reduce the bilge pump's output.

bubb2 · #6 (**permalink**) 05-05-2008

yes they do decrease the the discharge, but they do keep it cycling thanks dog

sailaway21 · #7 (**permalink**) 05-05-2008

But not if you oversize the check valve and bush it down to the discharge hose. (g)

Shortman · #8 (**permalink**) 05-05-2008

not timed, at the same level as the pump which may be the problem, probably should be above it a bit. Have had bottom screen off pump, impeller clear. Nature of construction is such that a bubble could get up into the impeller cavity. I don't remember, but I think there is a check valve. if there were not, the backflow would push out the air, but then risk short cycling.

Stillraining · #9 (**permalink**) 05-05-2008

I have check valves in all my bilge pumps even my gusher...with high mounted discharg through hulls, if you dont as soon as the pump shuts down you will get all that vertical line draining back into the bilge...If your worried about reduced flow add another pump to make up for it..I have 3