Pentair #8 Lock Washer | Dyna-Pro / Dyna-Pro E / Max-E-Pro / IntelliPro Pumps | U43-21SSZ

The Pentair #8 Lock Washer (U43-21SSZ) is the OEM replacement fastener for Pentair's Dyna-Pro, Dyna-Pro E, Max-E-Pro, and IntelliPro series inground pool pumps.

⚠️ IMPORTANT: QUANTITY REQUIRED PER UNIT — VERIFY BEFORE ORDERING
IntelliPro Variable Speed Pump models require 5 of this washer per unit. Dyna-Pro, Dyna-Pro E, and Max-E-Pro models require 1 per unit. Check your equipment's parts diagram to confirm the quantity needed before adding to cart.

This lock washer provides positive fastener retention under vibration, preventing loosening of pump assembly hardware during operation. The serrated teeth bite into the mating surface to maintain clamp load — a small but critical component in keeping pump internals securely assembled. Replace any lock washer that shows signs of flattening, corrosion, or deformation; a compromised washer will not provide adequate retention.

Specifications

Fits Into

Compatibility is based on Pentair parts documentation and available OEM records. This is not an exhaustive list. For certainty, verify the part number in your equipment's manual or on the original part itself before ordering.

Pro Tip

When disassembling your pump for any service — shaft seal replacement, impeller service, or motor swap — inspect every lock washer in the assembly. Lock washers are single-use by design: once the teeth are compressed or the washer has been torqued down, they lose their locking effectiveness. Replacing them at the same time as your primary service part costs very little and eliminates a common source of hardware loosening under vibration. For IntelliPro models, confirm you have all 5 washers on hand before beginning reassembly.