So you found a puddle of water under your sink and you cannot figure out where your the water is coming from.
The first thing to do is to clear out the cabinet under the sink. Clean up any water. Then let the cabinet dry out.
Now to figure out where that water is actually coming from.
Once the cabinet is dry, place some paper towels or a dry rag down on the bottom of the cabinet. Then without running the water. Wait 10 minutes or so and see if the towels get wet. A wet towel means more than likely the leak is on the water supply side of the faucet and not in the drain system.
The towels remain dry after a period of time, put a stopper in the sink drain and run some water in the sink. You notice the towels get wet doing this, chances are the leak is either in the faucet or around the drain basket and not in the drain piping, unless your stopper is not holding the water back. Likely, if the towels are wet towards the back of the cabinet it is probably the faucet leaking. If they are wet in the center, run your hand or a rag along the drain piping and check for water.
After doing all of this, the towels still remain dry, pull out the stopper and let the water drain out. If the towels get wet now, you most likely have a leak in your drain piping.
Head over to the Next Page to see how to repair these issues.