CAUTION!! - Before installing new filters, make sure that the water supply is turned off and the pressure has been released from the unit. This can be done by opening a pure water output line. Vertical Filters: (Mainly the pre-filters unless on a smaller unit): Unscrew the filter housings. Remove old filters from the unit. Install the new filters, making sure they're in the right order: Stage 1 - 10 micron sediment Stage 2 - 5 micron carbon block (normally) Stage 3 - 1 micron carbon block. Stage 5 - After the RO membrane and only if you have a vertical DI. Make sure to hand tighten the housings after installation. Too much tightening can lead to the housings cracking. In-line Filters: The in-line filters normally have push-in fittings. Simply remove the tubing and/or fittings from the filter. Remove the blue dust caps from your new filters. Then install the new filters making sure of the direction of flow. In-line filters can be used as pre-filters on smaller units, though they're mainly used as post-filters. The standard in-line filter is 5 microns. If you have a unit with the in-line filters as your pre-filters, the setup is as follows: Stage 1 - In-line carbon Stage 2 - In-line sediment The reason for this is the in-line carbon tends to release grains of carbon which can clog the RO membrane. The sediment follows after it to prevent this from happening. RO Membrane: Remove the old membrane by using either a pair of pliers or a screwdriver to put through the holes in the plastic center of the membrane. Make sure that the new membrane has its O-rings well lubricated. Install the new membrane with the O-rings in the housing first. These are basic instructions for standard filters and may not apply to all units.