Reverse Osmosis stems consist of a series of filters that require periodic maintenance. Three of the four filters are the Pre, Post and Inline, these filters are recommended to be changed once per year. The fourth filter is our Membrane, this filters responsibility is removing contaminants from the water. Dependent on water conditions, this filters are to be changed every three to five years. If you need filters or would like to have the Clean Water Center take care of your filter changes, give us a call today!