Hey Bin,
If you havent done this before, then follow this, shutdown the Valve first then open the faucet from both sides upwards and downwards. If you still need more information you can possibly get ... read more
What are some important questions one should ask a contractor when doing a remodel for the first time and what are some important signs to look out for?
Any honest contractor will provide you with copies of their State Licenses and Insurance so you can verify them. If they don't ask - if they hesitate - RUN!