DIY Network

Install an Under-Sink Water Purifier

This easy DIY project will quickly improve the taste and purity of your home's drinking water. Learn how to install an under-sink water filter with these steps.

More in Kitchen

installing an under sink water filter
  • Time

    Under Half Day

  • Price Range

    $1 - $50

  • Difficulty



Step 1: Disconnect the Water Supply

Below the sink, shut off the cold-water supply to the faucet. Use an adjustable wrench to disconnect and remove the tubing that connects the faucet and supply valve.

shut off cold water supply to faucet

Step 2: Connect the Water Filter

The filter is installed between the cold-water supply and the faucet, in the space where the rigid line was removed. Flexible supply-lines are usually included in the filter kit. Use one to connect the water supply to the filter inlet, and the other to connect the faucet tubing to the filter outlet (Image 1).

Wrap all male fittings with Teflon tape to ensure a watertight seal (Image 2).

Compression fittings, also included in the kit, are used to connect the flexible supply lines. Each fitting includes a compression nut, sleeve and ferrule (Image 3). When making a connection, seat the plastic (or brass) ferrule into the male receptacle and hand-tighten the nut. If water leaks from the fitting when you turn on the supply valve, use a wrench to tighten the nut an additional quarter turn.

Connect the flexible supply line from the water filter inlet to the home’s cold water supply (Image 4).

Connect the flex-line from the water filter outlet to the kitchen faucet tubing (Image 5).

Step 3: Install the Water Filter

Mount the canister to the back wall of the cabinet beneath the sink (Image 1). Make sure the canister is mounted high enough to allow sufficient clearance to remove the canister body when it's time to change the filter (Image 2).

Check and follow the manufacturer's instructions on the recommended frequency for changing the filter