I just installed new 1/2" nipples in the supply lines for a bathroom sink, along with new stop vales on each nipple. Now I have 2 leaks:

One where one of the nipples connects to the elbow joint inside the wall (In this case, the connection between the nipple and the joint is right at the surface of the dry wall). The 2nd is on the other nipple, where it connects to the stop valve. I wrapped each connection with what I'd call 1 1/2 rotations of teflon tape.

How tight should I have tighten each connection? Today I further tightened each hoping it would fix the leaks. No luck. Any suggestions? Could I have used too little tape? For the nipple/elbow leak, I suspected it could be the old pipe in the wall. But the nipple/stop valve leak is puzzling because it's a new nipple and new valve.

I'd be grateful for any suggestions.