Unscrew the impeller of the pump. Gently remove the rotating part of the seal by prying it up with two screw drivers. Take care not to scratch the motor shaft as you do so.
Remove the seal plate from the motor. Set it face down on a flat surface in a safe area where it won't be moved.
Push out the ceramic stationary seat washer from the seal cavity located under the seal plate with a screw driver.
Wipe off the polished surface of the new ceramic washer with a soft cloth. Flip over the seal plate so that the seal cavity is now facing up. Clean out the cavity with the cloth.
Dip the new ceramic washer in soapy water to lubricate it. Set the cardboard washer over the polished side of the ceramic washer. Press firmly down onto the cardboard and washer with a 3/4-inch socket until it slides into the seal cavity. Discard the cardboard washer. Check the polished surface of the ceramic washer and wipe off any excess soapy water or dirt.
Reinsert the seal plate. Be very careful while doing so as the ceramic washer is easily scratched and damaged.
Clean off the face plate of the sealing washer with a soft cloth. Dip the cloth into soapy water. Wipe the soapy water on the inner and outer side of the rubber drive ring to lubricate it. Slide the assembly onto the motor shaft with the seal face down so that it hits the shaft shoulder located in the center of the seal plate.
Place the impeller back onto the pump. Tighten the impeller screw until the impeller hub meets the shaft shoulder to create a strong seal with the sealing washer.