How to Install an Under-Sink Water Filtration System

Water filtration systems are the most effective way to upgrade the quality of your home's drinking water without relying on countertop pitchers. By installing a dedicated unit under your kitchen sink, you ensure a constant supply of filtered water for drinking and cooking while keeping your countertops clear and functional. Done well, this project is a straightforward plumbing task that yields immediate, noticeable results. You are essentially creating a bypass loop off your existing cold water line, running that water through a series of filters, and terminating it at a small auxiliary faucet. The process requires careful attention to thread sealing and leak testing, but it is well within reach for anyone comfortable with basic hand tools.

  1. Stop the Flow First. Locate the cold water shut-off valve under your sink and turn it clockwise until fully closed. Open the kitchen faucet to drain any remaining pressure in the lines.
  2. Mount Your Filter Faucet. If your sink doesn't have an existing hole, use a hole saw to drill a 1/2-inch opening through the stainless steel or countertop. Insert the faucet shank and tighten the mounting nut from underneath with a basin wrench.
  3. Tap Into the Water Line. Disconnect the flexible cold water supply hose from the shut-off valve. Screw the included T-adapter onto the valve, then reconnect the cold water hose to the top of the adapter.
  4. Secure the Filter Housing. Position the filter bracket on the side wall of your cabinet, ensuring there is at least 3 inches of clearance beneath the housing for future filter changes. Secure the bracket using the provided wood screws.
  5. Connect the Lines. Measure and cut lengths of plastic tubing to connect the T-adapter to the filter inlet and the filter outlet to the new faucet. Push the tubing firmly into the quick-connect fittings until you feel it click into place.
  6. Test for Leaks. Slowly turn the cold water valve back on. Check every connection point for moisture, then open the new drinking water faucet to flush the filters for 5-10 minutes.