We strongly recommend that you clean the filter every one to three weeks, depending on how often you use your spa. Never wait longer than a month to clean your filters. And remember that just because a filter is dirty, it does not mean that the filter needs to be replaced. Filters that are cleaned on a regular basis can last up to 12 months. In order to determine whether your filter cartridge needs replacing, look within the pleats of the filter for any build up of grime and dirt particles after cleaning it. If any dirt particles remain, the filter should be replaced. Keep in mind that filters are not designed to last more than 12 months.