How to replace mechanical seals in centrifugal pumps

Written by justin a. mann
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How to replace mechanical seals in centrifugal pumps
Replace the mechanical seal in your centrifugal pump to protect the pump from leaks. (Jupiterimages/ Images)

A centrifugal pump uses the principle of centrifugal force to move water through plumbing systems and hoses. The centrifugal pump spins a shaft at high speed which rotates an impeller, creating a vacuum through centrifugal force that pulls the water. A mechanical seal positioned just behind the spinning impeller on the motor shaft prevents water from entering the delicate electrical motor of the pump. Replacing these mechanical seals involves opening the pump system, removing the impeller from the pump's shaft and sliding the old seal off the shaft.

Skill level:

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Things you need

  • PVC saw
  • Wrench
  • Mechanical seal
  • PVC glue and primer

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  1. 1

    Turn off the centrifugal pump. Shut off the breaker supplying power to the pump. Cut the plumbing connected to the centrifugal pump with a PVC saw. Set the centrifugal pump down at a spacious work area.

  2. 2

    Unscrew the pump bolts around the pump housing with the wrench. Disconnect the centrifugal pump's motor from the wet end.

  3. 3

    Place the wrench over the motor shaft and hold it still. Rotate the centrifugal pump's impeller counterclockwise off the shaft. Take the piece of the seal out of the back of the impeller. Slide the remaining seal piece off the shaft.

  4. 4

    Place a new mechanical seal onto the shaft. Slide the mechanical seal along the shaft but be careful not to touch the front face of the seal with your fingers. If body oils get on the face of the seal, the seal becomes compromised and may not function properly.

  5. 5

    Hold still the shaft with the wrench and screw the impeller onto the centrifugal pump's motor shaft. Line up the bolt holes on the motor and wet ends of the pump, insert the bolts, and secure the pump ends together with a wrench.

  6. 6

    Place the centrifugal pump system back into place in the plumbing. Secure the centrifugal pump to the plumbing with PVC glue and primer. Allow the glue and primer to dry for at least one day before running the pump.

Tips and warnings

  • Check the mechanical seal on the pump monthly for damage to prolong the life of the centrifugal pump.

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