Servicing your Black & White Undersink Water Filter

Undersink water filters are basic, straightforward devices that need only a periodic cartridge change. Here's how you do it.

1. Turn off the inlet water using the inlet valve that comes with the filter or the main cold water valve. Open the ledge faucet on the water filter and lock it open. When no water comes out, you know you have the inlet turned off and you're ready to service the unit.

2. Place a towel or a pan under the unit to catch spilled water. Open each of the vertical filter vessels with the filter wrench. They open by turning the sump (the bottom part) counterclockwise. Remove the old filter cartridges and discard. If the cartridges are axial style (like KDC1.5 or AAL, for example), note which end was up on the old filter so you can point the new one in the same direction.

3. Lubricate the black O rings very lightly with silicone lube if possible (Vaseline is OK, but silicone is better).

4. Install the new cartridges. If there's a sediment filter, it goes first. After that, it doesn't matter a lot in which order the cartridges are placed. It's best to place some sort of carbon filter last. If in doubt, please call. Replace the filter sumps with their new cartridges onto the unit. Tighten with the wrench, but not too tight. Be sure they're snug, but don't over tighten. With carbon block or sediment cartridges (radial flow cartridges), up and down don't matter. With axial cartridges (with hard plastic bodies where the water enters one end and flows through the entire cartridge, place the narrow end up (up meaning at the end where the cap of the filter is). If you get the axial cartridge in upside down, you’ll discover it quickly because no water will come through the unit.

5. With the ledge faucet still open, open the inlet valve and let water into the unit. It will hiss and sputter for a while until air is expelled. This may take several minutes. Leave the faucet open and let the unit run to drain for 5 minutes or so, then close the faucet. The unit is now back in service. Sometimes the water will appear milky for a day or so after the change. No problem. It's just air trapped in the unit that has to work its way out. The water is ready to drink.