How to Install Plumb & Shower Base

Overview

Let’s face it. Showers are the bathing choice of just about everyone. So if your bathroom has become a family bottleneck because you don’t have enough shower stalls or the one you have is leaking, read on. We’ll show you how to replace a leaky base, replace a tub with a shower only or install an additional shower to handle demand. Preformed shower bases have vastly simplified the installation process. They’re virtually leakproof and are vastly easier to install than traditional solid mortar bases.

Still, setting a base can be challenging, especially when you’re remodeling older plumbing. In this article, we’ll show you how to rip out an old tub and replace it with a one-piece fiberglass shower base. We’ll walk you through the tricky parts, first how to relocate the drain just right, then the necessary venting. Next, we’ll show how to set a rock-solid base—one that won’t crack or leak down the road. Our step-by- step instructions will take you right up to the point where the walls are ready to finish. But we won’t go into those finish details here.

This is mostly a plumbing project. To take it on, you should be familiar with basic pipe joining techniques. Mostly this involves cutting and cementing plastic pipes and fittings. Don’t worry if you make mistakes. The materials are inexpensive and corrections are easily made by cutting out sections and installing new fittings and pipes.

Completing this job—getting the old tub out, reworking the plumbing and installing the new base—will take a Saturday at least, a weekend at most. If you have to run a drain line through joists or studs, we recommend that you rent a 1/2-in. right-angle drill and a 2-in. hole saw (or bit; Photo 6). Otherwise basic plumbing tools and hand tools are all you’ll need. Be sure to apply for a plumbing permit and have an inspection done at the rough-in stage (when everything is still exposed) and after everything is complete (wall surfaces finished, final hardware installed).

Planning the job

Start by deciding on the size of the shower base and ordering it. Delivery can take weeks, so don’t rip anything apart until the new one is in hand. If you’re replacing an existing base, simply get one the same size. If you’re replacing a tub with a shower as we did, there are more details to consider. You’ll have the fewest problems if you match the new base to the old tub’s width (the front of the tub to the wall). Go wider if you like, but you may have to replace flooring. Or you may overstep required minimum distances from toilets and sinks. You might have to shift the supply valve as well. Keeping the same tub footprint (or smaller) minimizes the hassles.

We replaced a 5-ft. tub with a fairly spacious 4-ft. base the same width as the tub. (See “Selecting a Shower Base,” below.) We framed a 1-ft.-wide filler wall at the end, which is a nice place to build recessed niches and shelves for shower supplies.

Now’s a good time to buy a new shower valve too, especially if your old one doesn’t have scald protection, as all new ones do. It’s a big project to replace a valve that fails after tile or wall panels are installed.

You’ll need an assortment of pipes and fittings for installing the new drain and for reworking water lines. Pick them up after you open up the floor and walls. At that point you can see what you need, plan the new drain and water supply runs and make a list of supplies. Make a sketch like Figure A to help you keep track of parts.