How do you replace bearing on water pump 0.5HP?

You first have to separate the motor from the pump chamber. Remove the impeller carefully, it usually unscrews opposite direction of rotation. (Be careful with the ceramic seal inside pump chamber, it's delicate. ) When the motor is separate, unscrew the end with contacts and carefully pull this aside.

-Whenever I do this job, I always replace BOTH bearings. For a bearing cost usually less than $15 it doesn't make sense to commit all this labour to change only the faulty bearing. (the other may go in a month or two then you repeat all the labour ) Pull both bearings and carefully insert both NEW bearings. Re-assemble everything in opposite order. Fit new gasket on pump chamber. Screw pump chamber together doing opposing screws after each other (imagine 6 screws in a circle, loosely do all 6 then tighten 1 then 3, then 5, then 2, then 4 etc. This way the gasket will be even as opposed to tight on one side (if it's a Jet-pump this is VERY important ! )