It helps to know the anatomy of your tub drain when it's partially blocked and it's time to clean it; the blockage could be in the horizontal section of pipe or it could have something to do with the operation of the stopper. If your tub has a stopper lever, and the blockage is in the P-trap, you may have to remove the lever and linkage to clear it.
Bathtub Drain Anatomy
Unlike a sink drain, a bathtub drain doesn't always drop directly to the P-trap; instead, there is often a horizontal length of pipe that leads from the strainer to a tee in at the end of the tub. The lever on your tub -- if there is one -- is connected to a linkage that lifts a weighted stopper to open the tee and allow the tub to drain. If your tub has a stopper in the drain opening, the linkage drops the weight onto a spring-loaded rocker arm to lift the stopper.
More often than not, a mixture of hair and soap in the horizontal section of the drain is responsible for slow draining, and it isn't difficult to clear -- although the experience is a bit unpleasant. If that doesn't clear the drain, the next step is to remove the linkage and snake out the P-trap. The linkage itself may be at fault -- if it's too long or too short, it may not allow the drain to open completely.
Step 1 Remove the strainer or stopper from the drain opening.
- If your tub has a pop-up stopper and lever, the stopper just lifts out of the drain -- pull it up and then toward the back of the tub to remove it.
- If your tub has a strainer, remove it by unscrewing the screw holding it with a Phillips screwdriver
- If your tub has a push-lock stopper, unscrew and remove it. You can usually do this by hand, but in some cases you may need adjustable pliers to grip it.
Step 2 Clear the area around the drain.
You'll probably find hair and soap clumped into an unappetizing mess and extending several inches into the drain. Pull this out with a plastic drain cleaning tool, a bottle brush or needle-nose pliers.
Step 3 Clear the horizontal part of the drain.
Push a 12-inch cable tie or something similar into the drain to test for obstructions. If you find any, clear them with a plumbing auger, or snake. Turn on the water and test the drain, and if it's still slow, remove the linkage and clear the P-trap.
Step 4 Remove and inspect the linkage.
Unscrew the lever faceplate from the side of the tub, using a flat-head screwdriver. Pull the faceplate out and lift it vertically to extract the linkage. Keep lifting until the weight on the end of the linkage comes out. Inspect the weight; if it's full of hair or corroded, it probably wasn't lifting all the way. You can correct this by shortening the linkage -- you do this by turning the adjustment nut clockwise, using pliers.
Step 5 Clear the P-trap
Insert the auger into the linkage opening and push it in as far as it will go. It has a direct path to the P-trap though this opening. Crank the handle when you encounter an obstruction to work the head of the snake through it. Retract the head and remove any debris it has collected. Repeat as many times as necessary to create a clear passage.
Step 6 Reassemble the stopper linkage.
Drop the linkage back into place behind the tub and screw on the cover plate. Close the stopper, fill the tub with 1/2 inch of water, open the stopper and check the drainage. If the tub is still draining slowly, it's probably because the linkage isn't properly adjusted. Remove it and make the adjustment. This is something of a trial-and-error process, so you may have to do it several times.