How to Replace a Bathtub Waste-and-Overflow Tube

The waste-and-overflow tube is the fitting on your bathtub that prevents the tub from overflowing by catching water that gets too high and diverting it down into the drain system. The opening for the tube is a round opening covered with a metal grate or cover that lies a few inches down from the top of the tub, usually near the spout at the front of the tub. Whenever you are installing or replacing a bathtub, replacing the waste-and-overflow tube is pretty much mandatory. And a waste-and-overflow tube can sometimes fail on an existing tub, so you may find yourself replacing it on a tub that remains in place.

This is sometimes an easy job, but in other cases it can prove to be one of the trickier plumbing repair jobs you will tackle. On an existing tub, gaining access to the overflow tube can be challenging, and the process for replacing the tube can vary greatly, depending on what type of drain pipes you have and how the fittings have been made. Chrome or plastic parts made with slip fittings can be relatively easy to replace, but if the fittings are soldered or solvent-glued, the process can be much more complicated than you'd expect. DIYers sometimes find themselves over their heads when trying to accomplish this project, so evaluate the situation carefully before you tackle it yourself.

Anatomy of a Bathtub Waste-and-Overflow Assembly

The waste-and-overflow unit is an L-shaped assembly that consists of a drain fitting that sets into the opening in the bottom of the tub, connecting to a short horizontal drain pipe that runs to a tee fitting. The top outlet on this tee connects to the vertical overflow tube that terminates at the overflow opening in the tub, while the bottom outlet on the tee runs to the bathtub's drain trap and branch drain. There are several connections you will need to make when installing the assembly: the bathtub's drain unit, the overflow cover plate, and the various fittings that connect the pipes.

Access Issues

Installing a new tub waste-and-overflow can be a bit of a project, so be prepared. If your bathroom is over an open basement or crawl space, you’ll be able to access the drain from underneath, which is easier. If you have a slab foundation there might be an access panel that allows you to work from behind the tub. If there isn’t one already there you may need to cut one in before you can get the old waste-and-overflow out and the new in. No matter which type of access you have, the steps are roughly the same.

Tools and Supplies You Will Need

The materials required to remove and replace a bathtub waste-and-overflow tube will depend on what types of pipes and fittings are present. You can buy individual parts for different parts of the overflow assembly, but it's usually easiest to buy a complete assembly that includes the bathtub drain fitting, the overflow tube and cover plate, the tee fitting, and both the vertical overflow tube and horizontal drain arm connecting to the drain fitting. If you are installing a new tub, the manufacturer may supply the waste-and-overflow; if you are replacing the assembly on an existing tub, look for one that closely resembles the old one. Waste-and-overflow assemblies comes in several forms, including styles that include an integrated stopper assembly and lever. The style you choose is up to you.

You may require some or all of the following:

• Tub drain wrench
• Screwdrivers
• Channel-lock pliers
• Bathtub drain and overflow kit
• Hacksaw or tubing cutter (if needed)
• Plumber's putty

Instructions

All of the following instructions will apply if you are replacing an overflow tube on an existing bathtub. If you are installing an overflow tube on a new bathtub for the first time, jump past the removal steps and begin with the installation steps.

1. Detach the Drain Fitting

   First, remove the drain fitting from the bottom of the tub. Depending on the style of drain assembly, this may require that you first unscrew a cover grid to gain access to the drain body. A drain wrench is then used to grip the drain fitting and unscrew it from the drain arm by turning counterclockwise.

2. Disconnect the Overflow Cover Plate

   Unscrew the cover plate on the overflow fitting, located on the front wall of the tub. There might be one or two screws to remove here. The cover plate should simply pull away but if there is a rubber washer, it may be hardened and require some effort in order to remove the cover plate.

3. Remove the Waste-and-Overflow Assembly

   From either behind or under the tub, detach the waste-and-overflow assembly from the drain pipes. This is sometimes as easy as loosening slip nuts on the drain pipes and sliding the assembly free, but if the pipes have been solvent-glued or soldered in place, it can involve cutting the pipes free with a hacksaw or tubing cutter. Think this through before making any cuts. Careful cutting will make it easier to install the new waste-and-overflow tube.

   • Note: You may want to change the drain trap under the tub at this time. Since access is difficult, it may be easiest to replace this part at the same time you are working on the overflow assembly.

4. Test-Fit the New Waste-and-Overflow Assembly

   Disconnect the components on the waste-and-overflow kit, and test-fit them on your tub. Some cutting may be necessary if the kit does not exactly fit the dimensions of your tub. Having someone inside the tub to help hold things while you get everything lined up will greatly simplify things.

   If necessary, cut the pieces to size. After cutting, dry-fit the pieces again to make sure the overflow tube and drain arm line up correctly. A waste-and-overflow using slip-joints is easy to line up because you can leave the washers and nuts loose while sliding everything into position. If necessary, extensions can be used on the tubular pipe to make the overflow tube longer.

5. Attach the Waste-and-Overflow Assembly

   Position the assembly in place, so that the top of the overflow tube aligns with the overflow opening on the bathtub and the horizontal drain arm aligns with the drain opening in the bottom of the bathtub.

   Depending on the type of kit you are using, making the connections may require simply slip fittings, in which slip nuts are tightened down with channel-lock pliers; or it may require using solvent glue to permanently weld the PVC joints. If you are making the connections with slip joints, secure the slip nuts loosely at this point.

6. Connect the Drain Fitting

   To connect the drain fitting, begin by applying a bead of plumber's putty around the flange of the drain opening from inside the tub. From beneath the tub, position the rubber washer around the threaded drain tailpiece, then slip the tailpiece up through the drain opening.

   Thread the drain fitting into the threaded tailpiece of the drain arm, then tighten it down with a drain wrench. This works best if you have a helper hold the drain arm in place from below the tub as you tighten down the drain fitting from above. The plumber's putty should slightly ooze out around the flange of the drain fitting as you tighten it.

7. Attach the Overflow Cover Plate

   Position the gasket for the overflow tube on the backside of the tub, between the wall of the bathtub and the mouth on the overflow tube. If the gasket is tapered, the thicker side of the gasket should face down. From inside the tub, position the cover plate over the overflow opening and secure it with mounting screws threaded into the screw openings on the overflow tube. Tighten the screws down securely, so that the gasket compresses slightly between the mouth of the overflow tube and the backside of the tub.

8. Test the Installation

   Wipe away any excess putty from around the flange of the drain fitting. Have your helper run water into the tub drain while you watch to make sure there are no leaks under the tub. Close the tub stopper and fill the tub with at least 3 or 4 inches of water, and then allow it to drain quickly to give it a good volume test. If your waste-and-overflow assembly includes a pop-up stopper and lever, make sure these are working correctly.