I bought this old house a couple months ago and the inspection came back clean. After I moved in, I noticed that there is this dripping noise comes out from under the kitchen sink every time I wash dishes. It sounds like water hitting the bottom of the sink and it slows down after I turn off the water, it stops a few minutes after the water is turned off. I checked under the sink but couldn't pinpoint the source; it must come from behind the kitchen cabinet. There's no water mark or wet spot under the sink. I also looked at the ceiling downstairs right beneath the kitchen but didn't see any sign of leak either. What could this be? Should I get a professional in to check this out?

This doesn't sound too serious, Do you hear the sound when the unit's filling or discharging? Does the DW discharge into a garbage disposal? Back to you, Tom

Could be pipe expansion. Try this-turn on CW only. Hear it? Now turn on HW only. Hear it? If only on hot, it is expansion of the piping as heated water flows through. Not to worry.

Sometimes a little water accumulates in a drain and slowly drips out (maybe your noise). To make sure it isn't anything under your sink I suggest you remove all of the stuff under there and wipe the area down dry. Then place some clean paper towel under the whole area. Carefully looking with a flash light try filling up the sink, releasing the water. Turn on the hot, then the cold etc.. Just to make sure you haven't overlooked something. Its kind of fun to do, and gives you some peace of mind too. Hope this was helpful.

I was thinking pipe expansion also. We all have heard copper pipes in older homes that have baseboard heat.