My spa uses two filters and they are quite large, 8.5" diameter by 10.5" height. I have a set of filters I recently bought and the filters that were in it when I bought it (don't know how old they are). What is your spa's gallonage, and how often do you clean the filters?
My spa is almost 20 years old; I bought it second-hand. It works great, but the filter compartment is inconveniently situated. The lid to the compartment is IN the tub, and when the lid is removed, the stuff trapped in the filter floats out. So I'd rather just change/clean filters upon draining, but I don't know if that's often enough.
Thx,
Jules