Service intervals will vary depending upon many factors such as water usage, soap usage, garbage disposals, etc. The filter should be serviced at least every three years. For maximum protection it should be replaced about every 50,000 gallons of effluent. For average residential applications this correlates to about 1 year of service. Because the water usage and configurations of systems vary quite a bit from area to area and even in the same area depending upon when a system was installed, it is recommended that the filter be inspected annually.