How To Replace a Bathtub Waste and Overflow Drain

There are many different types of tub waste and overflows. We will discuss the Watco 601 pp tub waste and overflow and others like it because they are so popular, relatively easy to install, and conform to the Uniform Plumbing Code.

If you have a tub that has been in place a long time, you probably have an old brass slip joint style tub waste and overflow installed on it. These are good units that last a long time. However, they don’t meet the requirements for the UPC when it comes to waste and overflows installed in enclosed spaces like ceiling or joist spaces. So, if yours has started leaking and you need to replace it, consider a waste and overflow unit similar to the Watco 601 pp or a Rapidfit tub waste and overflow.

If you are remodeling your bathroom, it’s a good time to replace that waste and overflow. If your tub sits on a concrete slab, the job may seem impossible but it’s not.

Remove the tub drain and overflow trim, all the necessary surround pieces, the sheetrock or lathe and plaster, and remove the tub. Set the tub on a solid surface and level it both ways. Now measure through the tub drain hole and determine how far it is from the solid surface to the inside of the tub at that location. Write that down, and measure the distance from the solid surface to the center of the overflow hole. Write that down, as well.

Using an ABS sanitary tee, cut a piece of 11/2” ABS pipe to fit from the top outlet of the tee to the overflow fitting. Now, cut a piece of the 11/2” pipe to fit from the side outlet of the tee to the drain fitting. Push fit those pieces together and try the waste and overflow on the tub. You will almost certainly need to make more than one cut on both pieces of pipe. This is very much a trial and error procedure. Make sure the overflow fitting meets the overflow hole in the tub squarely and the same for the drain fitting. If it fits well without further adjustment, go ahead and glue the pieces together with ABS cement, aligning the overflow fitting and the drain fitting to face each other and be parallel to the pipe they are fastened to.

Cut off the old p-trap in the hole in the floor and, using the measurements you took earlier, fit a new p-trap, install the new waste and overflow so that the top of the drain fitting is the proper distance from the floor’s surface, and centered to meet the drain hole in the tub. It’s best to cut and fit repeatedly, making small adjustments until you get it perfect, then mark the floor indicating the center of the tub drain fitting so you can install the glued-up assembly to your marks.

Pick up the tub and walk it into position. Lower it straight down over the tub drain until it sits firmly on its supports and the concrete floor. If everything has gone well, the tub drain and overflow match up perfectly with the respective holes in the tub.

Fold the tub drain gasket and work it into position on top of the drain fitting through the drain hole in the bottom of the tub. Putty the tub drain flange and screw it into place. A word of caution: the metal threads of the drain flange will easily strip the plastic threads in the drain fitting. Go slowly and carefully here or all your work will be in vain.

Fit the overflow gasket into place using the same method as described above for the drain fitting. Install the overflow plate with the mount screw observing the same precaution above. Trim the putty around the drain fitting and finish the rest of your tub installation.

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