The purpose of the drain saddle is to provide a drain for the RO unit. Water will flow from the unit's drain line, through the hole you drill and into the metal or plastic drainpipe under your sink.
First, choose a place to install the drain saddle. It can be installed on a horizontal or a vertical pipe. (The horizontal pipe is better because it assures noise-free performance.) Install above the J or P trap in the drainpipe. When you've selected the spot, drill a 1/4" or slightly smaller hole in the drainpipe. On horizontal pipes, drill into the upper half of the pipe. Attach the saddle around the pipe with the bolts provided so that water can flow through the fitting into the hole you have drilled. The Quick Connect elbow provided with the saddle can be removed to facilitate locating the saddle directly over the hole in the drainpipe. Reinstall the fitting after the saddle has been tightened onto the pipe.
Point the fitting toward the RO unit.
(whole house & well units)