Unicel UHD-SR50 Cartridge, 50 Sq Ft

The Unicel UHD-SR50 is the replacement cartridge element for Sta-Rite Posi-Flo filters, also referenced as TX-50. It measures 8-11/16 in across the outside diameter and 13-5/16 in long.

A note on the rating

The sources for this cartridge do not agree on filter area. The product name and description call it 50 sq ft, while the product attributes give 52 sq ft. Both readings are carried here rather than picking one. The dimensions are the dependable check: measure the element you are taking out and match it against 8-11/16 in by 13-5/16 in.

Getting the life out of it

Cartridges last longest when they are rinsed properly. Work a hose from the top down and spray between the pleats rather than across them, and leave the pressure washer alone; it forces dirt deeper into the fabric and cuts the media. A soak in cartridge cleaner once a season lifts oils and scale that plain water will not.

When to replace

Go by pressure rather than appearance. Note the gauge reading with a genuinely clean element, and when that starting number creeps up and stops returning after a wash, the cartridge has reached the end of its service life.