Hi Kammie,
I can't be sure just by looking at the photo, but that looks like it could be "soap scum", which is produced in a spa that has low hardness, pH and/or alkalinity. Is that residue sort of soft and flaky or gooey, or is it hard and brittle?
I assume you're using chlorine as a primary sanitizer, is that right? Any issues with water clarity?
Don
Hi Don,
Thanks for your quick reply. Here are some answers to your questions. The residue on the cartridge is hard and brittle. We do not use chlorine or bromine in the tub...just the mineral cartridge and a spa shock oxidizer once a week (the hot tub also has an ozonator). We have not had any issues with water clarity.
Kammie