After removing the screw, turn the hot and cold water black tap supplies and turn the cartridge through 180 degrees. Next, remove the decorative cap on the handle of the faucet and turn the handle by hand. To tighten it, you can use an Allen key or a Phillips screwdriver. Once you've done that, place it back in place. If your faucet is still leaking, it may be a sign of a corroded cartridge.