The answer to 'why is my drain leaking water' is that there is likely a problem with the drain pipe or the seal around the drain. Common causes include a crack in the pipe, a loose or damaged drain gasket, or a buildup of debris and mineral deposits that are preventing a tight seal.
Some common symptoms of a leaking drain include water pooling around the drain, moisture on the floor or cabinet underneath, and a musty smell from the drain. If the leak is coming from a sink drain, you may also notice the water draining more slowly.
For minor leaks, you may be able to fix the problem yourself by tightening the drain or replacing the gasket. However, if the leak is coming from a crack in the pipe or a more complex issue, it's best to call a professional plumber to diagnose and repair the problem properly.