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, sometimes covered with a metal grate or cover, that lies a few inches down from the top of the tub, usually near the spout. Whenever you are installing or replacing a tub, replacing the waste-and-overflow tube is pretty much mandatory.
Every tub is built a little different, and the drain can be located in different positions, which means you may have to adapt when installing a new waste-and-overflow. Sometimes the tub may even outlast the tub waste-and-overflow, forcing you to replace the drain system before you are ready to replace the tub.
Installing a new tub waste-and-overflow can be a bit of a project so be prepared. If you have a raised floor, you’ll be able to access the drain from under the house, 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 and the project is much easier with two people.
Start by buying a replacement waste-and-overflow tube. If you are installing a new tub, the manufacturer may supply the waste-and-overflow; if you are replacing only the waste-and-overflow on an existing tub, then look for one that closely resembles the old one.
Remove the Old Waste-and-Overflow Tube
- First, remove the drain fitting from the bottom of the tub. This may require a tub drain wrench. The drain fitting should just unscrew.
- Then, unscrew the overflow plate. There might be one or two screws to remove here.
- From either behind or under the tub, the rest of the tub waste-and-overflow can be unscrewed or cut out, depending on which type you have. Think this through before making any cuts. Careful cutting will make it easier to install the new waste-and-overflow tube.
- NOTE: You may or may not want to change the drain trap under the tub at this time, depending on how difficult everything is to get to. If you decide to change it, this is a good time to remove it.
Installing the New Waste-and-Overflow
- Dry-fit the new pieces. If your new waste-and-overflow tube is a PVC type, you will want to dry-fit it the pieces in order to line up the pipes and fittings perfectly before solvent gluing. Having someone inside the tub to help hold things while you get everything lined will greatly simplify things. Screw the tub drain fitting and overflow plate on to hold things in place while you take measurements.
- In necessary, cut the pieces to size. After cutting, dry-fit once again to make sure the overflow tube lines up correctly, because there will not much room for play once the waste-and-overflow is glued. A waste-and-overflow using slip-joint washers is easy to line up because you can leave the washers and nuts loose while sliding everything into position. Extensions can be used on the 1 1/2" tubular pipe to make the overflow taller, if necessary.
- Put the waste-and-overflow into place. The bottom drain fitting under the tub should be connected first. Rubber couplings are often used to help make the drain connections easier to put together. These are fine, as long as the couplings are accessible. Make sure to glue the fitting under the tub, if required.
- Attach the tub drain fitting. Once everything underneath is connected and glued to the right lengths, have your helper inside of the tub put plumber’s putty around the bottom of the tub drain fitting flange. Make sure the rubber washer goes under the tub on the opposite side of the drain fitting, over the tailpiece. Have your helper tighten the drain fitting from above while you make sure everything stays in position underneath.
- Attach the overflow tube. The bathtub overflow gasket goes on the back side of the tub. Have your helper inside the tube screw the overflow plate on while you make sure the gasket stays in place. If the gasket is tapered, the thicker part of the gasket goes on the bottom.
- Clean up and test. Remove 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, then allow it to drain quickly to give it a good volume test.