The Unicel 6CH-940AM is a 45 square foot top-load replacement cartridge for Waterway front access skimmers and the many spas built around them, replacing OEM part number 817-0050. It is a short, wide cartridge — 6″ across and only 8-1/4″ tall — and it fits 225 pleats into that compact body, the densest fold count relative to length of any cartridge in the Unicel range.
The AM in the part number stands for antimicrobial. The media is treated to inhibit the growth of odor-causing and stain-causing bacteria on the filter itself, which is what keeps a cartridge from developing that musty smell it can get even when it looks clean. It does not sanitize your water — your chlorine, bromine, or salt system still does that, and this cartridge changes nothing about your chemistry routine. It simply keeps the filter from working against your sanitizer between cleanings.
The connection is where this cartridge demands real attention. The bottom carries an injection molded 1-1/2″ SAE thread, and that is not the same as a 1-1/2″ MPT pipe thread even though the numbers read identically. SAE and MPT are separate thread standards with different forms and pitches. A 1-1/2″ SAE cartridge will not thread into an MPT fitting, and forcing one into the other damages both. This is far and away the most common ordering mistake on this cartridge, and it is worth thirty seconds of checking before you buy.
Above the thread, a semi-circular handle spans the closed top, giving a firm grip for threading the cartridge on and lifting it out without touching the pleats. Media is Unicel’s 3 oz polyester with antimicrobial treatment, over a solid injection-molded core with chemical-resistant end caps. Made in the USA by Meissner Manufacturing, with more than 45 years behind the Unicel name.
Pro Tip — check your thread type, not just the size. This cartridge uses a 1-1/2″ SAE thread. Other spa cartridges use a 1-1/2″ MPT pipe thread. The nominal size is identical and the two are not interchangeable. Here is how to tell them apart by eye: SAE threads are coarse — noticeably chunkier, with fewer, deeper turns, running straight down a cylinder of constant diameter. MPT pipe threads are finer, packed more closely together, and taper slightly so the fitting is a touch narrower at the tip than at the base. Hold your old cartridge up and look at the thread profile. If it is coarse and straight-sided, this is your filter.
Brand
UNICEL®
