Whirlpool filters consist of a special fleece which was developed to absorb a lot of grease and dirt. To remove the grease and dirt from the fleece you need a special filter cleaner.
SpaBalancer FilterClean Natural was specially developed for cleaning fleece filters.
Conventional filter fleeces consist of cylindrical fibers (right picture). In contrast, the Reemay® filter fleece (left) is shaped in such a way that as much dirt as possible can settle, but the water flow is not impaired. Normal filter fleeces clog much faster due to their shape and the water can hardly flow through.