The 30 in. Steel Sprinkler Valve Key is typically for turning off main outdoor water supply valves, which might be necessary if your under-sink shut-offs don't work or are absent. However, for most faucet repairs, you'll primarily use the smaller shut-off valves located directly under the sink. Always confirm the correct water shut-off point for your specific setup.

First, double-check that all connections are tightly secured but not overtightened, and ensure the new O-rings and seals are properly seated and are the correct size for your faucet model. If leaks persist, the valve seat itself might be worn and require replacement, or the faucet cartridge could be faulty, necessitating a different repair kit.

Always turn off the water supply completely to prevent flooding, either at the specific faucet's shut-off valves or the main house supply. Plug the drain opening to avoid losing small parts like screws or O-rings down the drain, and consider wearing safety glasses to protect from potential splashing or debris.

To stay within the estimated 2 hours, have your repair kit, tools, and a clear, well-lit workspace ready before you begin. Take photos during each step of disassembly to aid in reassembly, which is especially helpful for beginners. If you encounter unexpected difficulties like corroded screws, a quick online search for your specific faucet model can often provide targeted solutions.