Bilge Pump Mystery

[andantesail]

Suddenly my bilge pump won't pump out the last few (=/- 8 inches) of water, thus leaving the float switch on. I've replaced the pump (checking polarity) the problem persists. Switched back to the other pump. Same thing. I've used a water hose to shoot water up the exit hose and out the thru hull. Still have the problem. I'm flat out of ideas other than to replace the exit hose, but I don't find any leaks in the current one. Any suggestions would be much appreciated.

Thanks
Karl
Andante PSC 34 #276

[sailingdog]

If the impeller has broken free of the hub, is slipping on the spindle, or is missing some blades, you might have this problem. When the water is higher, it requires less pressure from the pump to move it, since the water outside the pump, in the bilge, is adding pressure to the hose.

[Omatako]

Originally Posted by sailingdog

If the impeller has broken free of the hub, is slipping on the spindle, or is missing some blades, you might have this problem. When the water is higher, it requires less pressure from the pump to move it, since the water outside the pump, in the bilge, is adding pressure to the hose.

. . . . . but the pump has been replaced . . . . .

[sailingdog]

Has he checked the voltage at the pump end of the wiring? If the voltage is low, you'd have similar issues.

[remetau]

Maybe you had a one way valve in the hose that has gone bad letting the water in the hoses drain back down, but I would think that the pump would shut off at least until the water level hit the switch level.

[sailingdog]

Originally Posted by remetau

Maybe you had a one way valve in the hose that has gone bad letting the water in the hoses drain back down, but I would think that the pump would shut off at least until the water level hit the switch level.

If the impeller isn't spinning fast enough, the centrifugal type pumps, which most small integrated submersible bilge pumps are, aren't going to push water very well. The fact that he's changed pumps and that there isn't a problem with water going through the hose, makes me think it is voltage related.

[jrd22]

That's kind of what I was thinking Rem, that maybe the vented loop was plugged before, creating a siphon out of the bilge at the end of the pump cycle, but now it's allowing the water in the hose to drain back into the bilge. If the pump runs continuously though I can't figure why it wouldn't pull the level down to where it would shut off until the water drained back in.

Edit- SD, you are probably on the right track. Low voltage would drastically reduce pump performance.

[oceanscapt]

Many pumps have a maximum lift spec. Could the difference be higher than that? When the bilge is heavy with water, the pressure will generally ovecome the lift difference or worn pump parts.

[LakeSuperiorGeezer]

Bad float switch, or is that built into the pump?

[brokesailor]

Check valve stuck shut?