How to Fix a Leaky Tub Drain

A plumber holding a wrench trying to fix a leaky drain.
What You'll Need
Drain stopper
A helper
Mastic putty
Shoe removal tool
New washers
Channel lock pliers
Paper towels
New compression joints
Pipe dope
New pipes
New fixture

A leaking tub drain can be very damaging to the surrounding floor as well as the ceiling of any rooms below the bathroom, so quick action is important. However, you can save yourself some money by fixing a leaky tub drain yourself. Don’t try to get away with a quick fix. It is best to replace what is malfunctioning rather than using a product which claims to fix leaks fast and easy.

Step 1 – Find the Leak

Put a drain stopper in the tub and fill with at least six inches of water. Then, lay a few pieces of paper under the pipes you suspect the water are leaking. Have a helper remove the stopper while you shine a flashlight on the drain. You should be able to confirm whether the drain itself is leaking if you see water on the paper. Then, locate the leak by tracing the dripping back to the source.

Step 2 – Reseal the Drain

You may determine that the seal holding the drain to the tub has gone bad over time. If this is the case, you might be able to use putty to reseal the joint before you replace the fitting at the base

If the leak is from the tub shoe, deeper in the drain, you need the shoe removal tool pull it out. Put plumber’s putty around the bottom of the shoe and reinstall it. Make sure to check the washer between the bottom of the tub as well as the actual tub shoe. If its damaged, replace it. It's usually not, but check it anyways to be safe. When you reinstall the shoe, putty will push out from the shoe. Keep tightening it until its secure and wipe the excess putty away. Then, fill the tub and check for leaks to see if the problem is fixed.

Step 3 – Tighten Any Joints

It is more likely that the leak is coming from a loose or ill-fitted joint. Try tightening the joint and see if this will stop the leak. Also check all the washers and replace any which seem to be damaged or old before you test for leaks again by filling the tub and letting it drain. Dry off the joints with a paper towel before doing the test so you don't end up with a false positive. While your helper is releasing the drain in the tub, hold a dry paper towel against the joint. If the towel becomes wet, you still have a problem, and you may have to completely replace the joint.

Tip: It would be a good idea to use pipe dope when you remove the nut. Be generous when applying the dope to the threads where the nut screws on, and tighten it back.

Step 4 – Replace the Waste Fitting

If the problem is the waste fitting itself, you need to completely remove the piping from under the tub. It is best to replace the unit rather than trying to fix it. This is recommended if the problem is in the waste trap or sump of the drainage system as well. Unless you're very experienced with plumbing and piping, this job is best done by a professional.

Mark Vander Sande, professional plumber, contributed to this article.