Before attempting to change the o ring on your Nivito kitchen faucet, be sure to remove the retaining clip. You may also need to remove the spring from the faucet. Afterward, you'll need to remove the retaining clip. Next, you'll need to disassemble the faucet from handle to cartridge. You can use the tool to turn the water on and off. You can also replace the O-ring by following the instructions carefully.