We recommend calling us to schedule proper annual maintenance, which includes testing your membrane for TDS reduction and sanitizing your system, but if you are handy and want to do the job yourself, just follow these instructions for ordering online. If you have any questions, call us at 855-3M-Water. Below are filters you are due to replace. Simply click on any of the three then choose add to cart. The other two filters will appear under “YOU MAY ALSO BE INTERESTED IN...” Add them both to your cart and proceed to checkout.