A leaking bathtub drain causes extensive damage to the subfloor underneath the tub if left to leak for an extended period. Bathtub drains are sealed when they are put in; you have to break the seal to remove the drain from the tub. Before breaking your old drain, you will have to check the drain stopper for leaks. Replacing the drain stopper first and then the drain will ensure no new leaks appear.
Place a rag into the drain to catch screws.
Remove the screws holding down the drain lever plate that is on the wall of the tub under the faucet.
Pull out the lever with the linkage. Grab the linkage with a pair of pliers if it is not attached to the lever.
Attach the linkage to the stopper using a pair of pliers to tighten it. Test the stopper by filling the tub with a little water. If the tub still leaks, you need to replace the drain.
Fill up a bucket with water. Then turn off the water to the tub by turning the water valve to the off position.
Open the access panel behind the tub and inspect the PVC pipe. Tighten the connections using a wrench where leaks occur. Pour a little water down the drain to see if it still leaks.
Remove the connection that is leaking and inspect the threads. Cut a new length of PVC pipe if the threads of the old pipe are worn, using PVC pipe cutters. Cut the new PVC pipe to the same length as the old pipe.
Cover the threads with plumber's tape and reconnect. Pour more water down the drain and check for leaks.
Insert a basket wrench into the bathtub drain and turn the drain to remove it if the drain is the leaking culprit. Cut a notch into the drain with a hacksaw if the drain will not move. Insert a chisel into the notch and lightly tap it with a hammer to remove the drain. Assemble your new drain by placing the rubber seal around the end, then screw it into the bathtub.