The answer to 'why is my pipe leaking water' is that there are several common causes, including worn washers, loose fittings, corrosion, or a crack in the pipe. Leaks can be identified by water dripping, damp spots, or mold growth around the pipe. The solution depends on the cause, but may involve replacing washers, tightening fittings, or repairing or replacing the damaged section of pipe.
If the leak is minor and you feel comfortable doing some basic plumbing work, you may be able to fix it yourself. However, if the leak is severe or you're unsure of the cause, it's best to call a professional plumber. They can diagnose the problem and make the necessary repairs to stop the leak and prevent further water damage.