I perceive you may be talking about the sink faucet. The neck usually has an "O-ring" or two around it and a collar that slips over the neck and screws onto the base. If this is the case you could take it apart again and inspect the o-ring(s); if it/they are in good shape you need to carefully adjust the torque on the collar. If it is too lose you get a leak; too tight you damage the o-rings and cause a leak also. There is a range of "happy medium" there and it will work just right, allowing the neck to swing from side to side and preventing any leaks. I realize you may have been talking about something entirely different but this is the picture that was painted in my mind; let me know how it turns out for you.