Pentair Split Lock Washer, U43-12SS

The Pentair U43-12SS is a split lock washer used in Pentair pump assemblies. It is the genuine Pentair part.

Where it appears

Pentair lists it on the WhisperFlo XF parts diagram and on the IntelliFlo XF VSF and IntelliFlo XF VS diagram covering units manufactured after August 2015.

What it does

A split lock washer is a sprung ring with a gap in it. Tightening the fastener compresses the ring, and the spring load it stores is what keeps the fastener from vibrating loose on a running pump. Once the washer has corroded or been flattened permanently, it has no spring left and is doing nothing, so it should be replaced rather than reused.