Problems with a leaky bathtub are often traced to the overflow tube, or overflow drain assembly. The overflow tube is a safety feature that channels water that has overfilled the tub back down into the drain pipes before it can spill over the edge of the tub. But if the fittings on the overflow tube become loose, it can allow water to spill out and drip beneath the tub, where it might even ruin the floor or the ceiling in the room below the tub.
When a tub leak appears, often the impulse is to tear out the ceiling from below in an effort to fix the drain trap, when in reality, it may be the overflow tube that needs tightening or a replacement gasket. The overflow drain is very likely the source of your leak if you routinely bathe with the water level quite high, or if you have active children who slosh water playfully while they bathe.
The following steps can help confirm that the tub overflow drain is the source of a leak and show you how to repair the problem.
Equipment / Tools
- Utility knife
- Rubbing alcohol
- Replacement overflow gasket (as needed)
- Silicone caulk (as needed)
Confirm the Source of the Leak
Perform a quick diagnostic test to confirm that the overflow is the cause of the leak. Remove any access hatch or panel you have to expose the tub's plumbing connections. Run water in the tub and look for any water leaking directly below it. If you see water leaking, it is very likely you have loose connections in the drain fitting or the drain trap below the tub. Tighten or repair them as needed.
If running water in the tub causes no leaking, run the shower water instead. If you see leaking, look for signs of water splashing onto the tub spout, showerhead or faucet escutcheon plate (valve plate). Cracked or missing caulk around these elements lets water behind the shower wall.
If the shower test does not reveal leaks, then the overflow tube is the most likely culprit.
Check the Overflow Gasket
A tub overflow pipe seals against the tub with a ring-shaped gasket that typically lies between the flange around the pipe opening and the backside of the tub wall. The gasket is made of neoprene or rubber and can become brittle and cracked over time, leading to leaks.
To check the overflow gasket, remove the overflow plate by removing the screw or screws holding the plate in place and pulling off the plate. You may need to cut away caulking from around the overflow plate before it will come off. Cut the caulk with a utility knife.
Inspect the gasket. If it is heavily worn, cracked, or compressed, replace the gasket using the following steps. When in doubt, it's a good idea to replace the gasket to rule it out as a source of leaking. During the inspection, you may find that the overflow pipe assembly is loose or damaged. If so, it is an easy fix to replace the entire overflow assembly with new parts.
Some overflow plates are attached to the stopper assembly for the tub drain. In this case, carefully pull the assembly up and out of the drain opening. Most assemblies have a long, thin rod connected to a cylindrical stopper at the bottom.
Remove the Old Overflow Gasket
Replace a worn or damaged gasket by first removing the old gasket. The overflow drain pipe usually has a little give, and you can push it backwards (away from the tub) gently to gain some space to grab the gasket with your fingers or needlenose pliers. Remove all of the old gasket, then clean around the tub hole and the drain pipe flange with a rag and rubbing alcohol to remove all grime and residue.
Install the New Gasket
Push the new gasket into the hole in the tub wall and carefully fit it against the flange around the opening in the drain pipe. Make sure it is fully seated against the flange so that it will make an even seal against the tub.
Note: Overflow gaskets are often tapered to accommodate the angle of the tub wall; follow the manufacturer's instructions for how to work with the taper.
Reinstall the Overflow Plate
Fit the overflow plate back into position, making sure its opening (where the overflowing water flows out) is at the bottom. If the plate has a stopper assembly, carefully slip the stopper into the overflow pipe and slide the rod down until the plate meets the drain opening.
Secure the plate with its screw or screws. If there are two screws, tighten them a little bit at a time, alternating back and forth so that the gasket is compressed evenly against the tub.
The best way to test the new gasket (or other repairs to the overflow) is to fill the tub all the way and let the overflow do its job; that is, let some water overflow into it. So as not to waste many gallons of water, you can wait to do this until the next time you take a bath.
Tub Overflow Troubleshooting Tips
If the overflow gasket is in good condition or if replacing the gasket does not seem to stop the leak, there are some other approaches you can try:
- Make sure the gasket is installed correctly and that it sits in the center of the tub overflow drain.
- Inspect the edge of the tub around the overflow plate for nicks or corrosion that can allow water to seep in behind it.
- Check to make sure that the overflow plate is screwed tightly into place and that the notch in the plate is facing down.
- Check the seal on other shower parts, and apply new caulk as needed to ensure water can’t get behind the shower surround.