How do I open up a square flange pump?

Question

I have a square flange water pump being used as a sewer pump, it s a sideways mounted AO Smith C48D47Z01, but if you google search for  square flange pump  you ll see the type of pump it is.

Anyways, when I flip the switch to turn it on, the pump will hum for about 10 seconds without spinning up, and then throw the breaker. I m guessing that maybe the impeller is jammed?

I ve removed the 4 bolts that hold the motor onto the pump area and I can rotate the motor housing, but can t figure out a way to seperate the motor and get at the impeller. Can anyone hazard a guess at how I might be able to do this?

Spock (rhp) · Accepted Answer

you can't open it that way.  the impeller screws onto the end of the pump shaft, so the only way to remove it is to disassemble the pump.  [yeah, i know ...]

take the end cap off the motor -- it usually just a couple of screws and then pries off.  this exposes the electrical connections.  more important, it also exposes the end of the shaft.  on some motors, the shaft end is in plain sight and has a large slot for a major screwdriver in it.  if you can see that, you want to try to turn the shaft by hand with a screwdriver -- if it turns fairly easily, the impeller is not jammed and the problem is the pump motor.

if you can't see the end of the shaft easily, there is probably a triangular shaped electrical bracket covering it.  this can be removed with a nut driver or screwdriver -- the screw is frequently on the bottom side where it is difficult to see.  after that, the end of the shaft is visible and you can try to turn it.

should you discover that the motor has died, it may have to be replaced.  that requires disassembling the pump so the impeller can be removed.  [Of course, if the shaft is jammed tight and can't be turned, you have to disassemble the pump to get at the impeller anyway.]

the one time it doesn't have to be replaced is when the run/start capacitor has died and needs replacing.  since you say it humms ... this might well be so.  pump repair guy can test the run/start capacitor in place and put in a new one if that's the problem.  same guy can disassemble the pump to replace the motor or clear a jam.

in my area, the repair guy gets about 75 USD just to diagnose the problem.  He works for either a swimming pool supply outfit, an irrigation outfit, or a septic tank service.  [since this is being used for sewer, i'd start with septic tank service ... the other guys might not be willing to deal with it because of the use it is being put to.]

AndyF · Answer

Maybe tap the flange lightly in an even pattern using a piece of wood to prevent cracking the flange. The motor shaft is a tight fit into the pump and may be stuck. I have had a problem with a surface mounted well pump. 
If possible try flushing the pump backward with water pressure. It may blow out the obstruction. Power disconnected .  A few turns backwards won't hurt the motor. AO Smith electrical has replacement parts if needed.

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How do I open up a square flange pump?

2 Answers