This morning there is a rapid tapping coming from my kids bathtub drain. It's very steady and fast. I can hear it from within 10' of the bathroom door. It's very odd. Just so happens I had a plumber here this morning replacing my water heater so I had him look at it and he had no idea. Said he'd never seen that before. Water runs and drains fine and has no affect on the mysterious noise. Doesn't sound like it's echoing up from the sewer or anything and it's the only place we hear it. This is a ranch style home on a concrete foundation.

Any ideas?? We had a lot of rain yesterday and it's extremely windy today but the noise does not fluctuate with the wind.

Is this sound constant 24/7 or does it happen during or after water use? I know that you said that water runs and drains fine and has no effect on it, but try to notice if there is anything about your lifestyle that may give us some help. Without being there we need more details.How long has this been happening? Has there been any other work done in the house recently?

No response for a while so we could guess that what was happening was the new water heater would fire hotter than the previous tank. The dripping noise that you heard was actually the hot side pipe in the wall "ticking" similar to a drip noise. The ticking is caused by a tight spot that the pipe passes through and as the pipe heats it expands. The pressure of the pipe expanding slightly is the culprit. After the tub/shaower was used the ticking would continue until the pipe cooled down.

I have got the same problem. Rapid, tapping sound coming from my bathroom tub drain upstairs. The noise does not come from any other place in the house. There has been no work done recently on the plumbing (2-3 years). I do not have a new hot water tank nor do I need one. Any ideas?

Could be expansion and contraction, however I'd feel more comfortable if the noise were coming from a wall rather then from a drain. Let's see if I can add a few more possibilities.
Could this be a blocked and the sound you hear is air being sucked through the trap seal. **OR** could it be a very small leak from the spout seep down to the drain a dripping into the trap. Just a thought. Tom