if your tub has the type of stopper that has the operating lever on the end (usually under the spout) the problem may be that hair and scum have accumulated on the spring. There may be two screws attaching the lever plate to the tub. Remove these and pull the whole unit out. Will be a hinged rod and spring. spring is about 3-4 inches long. clean spring and put back in. You may have to move lever up and down to seat it properly when putting it back in. Normally when this spring gets hair and soap scum attached it will result in a very slow drain. I suppose as it gets worse it could completely clog.
sugway, July 2004