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Pentair Centrifugal Pump Shaft Seal | U109-433SS

Pentair SKU: U109-433SS

Pentair Centrifugal Pump Shaft Seal | U109-433SS

Pentair SKU: U109-433SS
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Pentair U109-433SS Shaft Seal (1-1/4") – For Sta-Rite C/CC Series & D Series Commercial Pumps (3 HP & 5 HP)

The Pentair U109-433SS is a replacement mechanical shaft seal (commonly referenced as a 1-1/4" shaft seal) used in select Sta-Rite / Pentair commercial pump models. This seal is installed where the motor shaft passes through the pump seal plate to help prevent water from leaking along the shaft into the motor. Replacing a worn shaft seal is a common fix for pump leaks that appear at the motor-to-pump connection area.

Key Details

  • Part Number: U109-433SS
  • Part Type: Mechanical shaft seal
  • Seal Size: 1-1/4" (commonly listed)
  • Typical Seal Material: Buna (rubber components) with standard mechanical seal faces
  • Primary Function: Helps stop leakage at the motor shaft / seal plate area
  • Replaces: U109-220 (older part reference)

Common Compatibility

  • Sta-Rite / Pentair C Series and CC Series centrifugal pumps (commonly 3 HP & 5 HP applications)
  • Pentair D Series commercial pumps
  • Important: Always confirm your pump model and horsepower using your parts diagram to verify this exact seal is correct.

Common Signs the Shaft Seal Needs Replacement

  • Water leaking from the area between the pump and motor (seal plate / motor bracket area)
  • Dripping or spraying that increases when the pump is running
  • Repeated moisture around the motor base (after confirming it is not plumbing-related)
  • Seal replacement is recommended any time the pump is opened for major service (impeller, diffuser, seal plate)

Installation Notes

  • Turn off power at the breaker before servicing the pump.
  • Mechanical seals have precision faces—keep them clean and avoid touching the sealing faces with oily/dirty hands.
  • Inspect the shaft sleeve and sealing surfaces; a grooved or corroded sleeve can cause a new seal to fail early.
  • Verify there is no wobble in the motor bearings; excessive shaft play can shorten seal life.
  • After reassembly, confirm the pump primes normally and check for leaks during the first run.

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Installation & Maintenance Tips

  • Fix the cause, not just the leak: Overheating (running dry), poor water chemistry, or misalignment can shorten seal life.
  • Replace the shaft sleeve if needed: A worn sleeve can cut into a new seal and cause repeat leaking.
  • Keep the pump from running dry: Loss of prime can overheat the seal faces and damage the seal quickly.
  • Address drips early: A small leak can lead to motor damage if water reaches the bearings or electrical components.
  • O-ring lube note: Use silicone lubricant on housing O-rings/gaskets only—do not grease mechanical seal faces.
Questions about returns? View our return policy.

Hours Of Operation:

Monday - Friday: 7:00 am to 5:00 pm Phoenix Time

Saturday: 8:00 am to 2:00 pm

Sunday: Closed

  • We do not ship on Saturday or Sunday.
  • Orders totaling more than $300 will require signature confirmation upon delivery.
  • We process and prepare orders for shipment within 1 business day. Please note that many other pool supply retailers require 3–5 days of handling time before shipping.
  • Orders placed after 1:00 pm Phoenix Time may not be eligible for same-day shipment.
  • Expedited shipping options are available at checkout.

Return Policy:

  • Products that are received damaged will receive a refund in store credit.
  • Most products are eligible for return within 30 days of receipt, except where noted below.
  • To initiate a return, please complete an RMA form prior to sending your item back.
  • Original shipping costs are non-refundable and will be deducted from the return credit.
  • Items returned missing accessories or original packaging, or that are not in the same condition as received, may be subject to a restocking fee of up to 100% depending on the condition of the item upon return.
  • Some returns will be charged an automatic 15% restocking fee.
  • We are unable to issue refunds for items that have been damaged or rendered inoperable due to installer error.
  • Please complete the return form to receive your RMA number and return shipping label.
  • Chemical products are not eligible for return under any circumstances.
  • The Pentair Colorsync 618031 is not eligible for return.
  • Pool cleaners are not eligible for return.
  • Opened seals and o-rings are not eligible for return.
  • Capacitors are not eligible for return.
  • Plastic popup tools are not eligible for return.
  • Automation components and circuit boards are not eligible for return.
  • If a light is returned due to a reported malfunction and is found to be fully operational upon testing, return shipping costs and a restocking fee will be deducted from the refund.
  • Orders refused at the time of delivery will be subject to the original shipping costs being deducted from the refund.
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