Unicel C-8399 Replacement: Compare 2 Options

How to measure your filter cartridge

If the number on your old cartridge has worn off, or you want to check a replacement for the C-8399, measure these four things and compare them with the product page.

1. Length: from the outside of one end cap to the outside of the other. Leave out any handle.
2. Diameter: across the end cap at its widest point, not across the pleats.
3. Top and bottom openings: note whether each end is open (measure the hole), closed, threaded (for example 1-1/2 in male thread) or has a handle. Both ends must match.
4. Filter area: printed on the label or end cap in square feet. A replacement should have the same area to fit your filter's flow rating.

Maker's cartridge vs aftermarket: the C-8399

C-8399 is a Unicel cross-reference number. 2 brands sell a filter cartridge listed as its replacement, including Wowreed, Yoozell.

• Maker's own part: made and sold by the equipment maker (for example Hayward or Pentair). Usually the highest price.
• Cross-reference and aftermarket parts: Unicel, Pleatco, Filbur and others make parts to the same size and specification and publish the matching numbers. Usually cheaper; materials vary by brand.
• Before you buy: compare the size, both end openings and the filter area with your old part, and confirm your filter or spa model on the product page.