Wondering how to replace a shower valve when valve access is bad or nonexistent, when the old pipes are galvanized steel, and when you want to go from a two-handle to one handle valve with temperature-balancing and anti-scald features? We show you how to solve these common problems.
By the DIY experts of The Family Handyman Magazine
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A full day
Overview: 3 common shower valve replacement problems
If your bath or shower faucet drips, you can fix the old shower valve and faucet with a few inexpensive replacement parts. (If the spout and handles are worn, you can change them out, too.) But if it’s a new style you’re after or features like preset temperatures or anti-scald protection, it’s time for replacement. How to change shower fixtures and installing a new shower faucet is a straightforward process of connecting the new valve to the old pipes. Sometimes all you need are the manufacturer’s instructions and some basic plumbing know-how. But it isn’t that easy very often. This article will focus on three complications that installation manuals and plumbing books ignore.
There’s no access to the inside of the wall.
The old pipes are galvanized steel.
You want to replace a two-handle faucet with a single-handle model.
Problem 1: No access panel
Photo 1: Mark the location
Punch a hole into the wall behind the faucet to mark the location of the access panel. Just slip a long screwdriver alongside the tub spout nipple and push.
Photo 1A: Location on back side wall
Poke a hole from the bathroom side. Don’t try to measure and guess.
Photo 2: Cut an access hole
Cut a hole 3 in. smaller than the access panel so you can see the exact pipe locations. Then mark and cut the full-size access hole.
Photo 3: Mount the access panel
Glue the access panel’s frame into place and snap on the cover after you’ve installed the new faucet. You can paint the panel to match the wall.
To replace the faucet, you have to work inside the wall. Some homes have a removable panel in the next room behind the faucet. If you don’t have an access panel, you might be able to replace the faucet by cutting a hole in the shower surround (Problem 3 below), but the best solution is to install a paintable plastic panel behind the faucet. You’ll find them in various sizes at plumbing suppliers, some home centers or online (search for “access panel”). Buy a panel that’s at least 14 x 14 in. If you don’t want to install a panel because it would be an eyesore, an oversized cover plate inside the shower surround is another option (Problem 3 below). If you already have an access panel but it’s too low to provide easy access to the faucet, you can install a second panel above the existing one.
Don’t try to position the access hole by taking measurements. Instead, remove the tub spout or faucet handles and punch a marker hole through the wall (Photo 1). If the wall is plaster rather than drywall, use a drill and a long bit instead of a screwdriver. Before you cut a hole sized for the access panel, cut a smaller hole (Photo 2). That way, you can see exactly where the pipes and valves are located and position the full-size hole for best access to them. Use the access panel frame as a template to mark the full-size hole. To avoid damaging the frame of the panel, install it after you’ve replaced the faucet (Photo 3).
Unscrew the ring nuts that fasten the union fitting to the faucet body. Then unscrew the union fittings from the supply lines.
Photo 2: Cut the shower riser
Cut the shower riser with a reciprocating saw or jigsaw. Cut slowly and gently so you don’t loosen the connections above.
Photo 3: Add a galvanized pipe coupler
Connect the cutoff shower pipe using a coupler designed for galvanized pipe. The coupler won’t work with copper pipe, so screw a short galvanized steel nipple into a copper fitting.
Unlike copper or plastic, steel pipes are joined with threaded, screw-together connections. So you can’t simply cut the hot and cold supply pipes. That would remove the threaded ends and you’d have no reliable way to connect new pipe.
To preserve those threaded ends, unscrew the union fittings that connect the supply lines to the faucet (Photo 1). You can leave the spout nipple connected to the faucet and remove it along with the valve. If the faucet is connected to a showerhead, cut the “shower riser” pipe (Photo 2). This pipe isn’t under constant pressure, so you can reconnect it with a special coupler later.
Connect the new faucet as shown in Photo 3. To connect the cutoff shower riser, use a special compression coupler designed for galvanized steel pipe (called a “Dresser” coupling). For a better seal and easier installation, apply Teflon pipe sealant to the coupler’s threads and rubber seals. Run the shower and check the coupler for leaks. If you find one, tighten the coupler’s nuts.
Figure A: New Shower Valve Connections to Galvanized Pipe
Make the connections shown when going from old galvanized pipe to copper pipe and adding the new valve. Also add new shutoffs.
Problem 3: Replacing two handles with one
Photo 1: Cut the tile
Cut a hole for the new valve using a rotary tool equipped with a tile-cutting bit. Mark the cutout using the cover’s paper template and a crayon.
Photo 1A: Tile cutting bit
A tile bit in a rotary tool cuts through most ceramic tile.
Photo 2: Install the new valve
Solder in the new valve. Use the paper template to make sure the valve is centered in the cutout.
Photo 3: Mount the cover plate
Mount the oversized cover plate. Install the faucet’s standard cover plate over it.
Shower Faucet Replacement
If you have a two-handle faucet, it’s easiest to replace it with another two-handle model. If you want the convenience of a single handle, you’ll have to hide the two holes left by the handles. An oversized cover plate does just that. Plus, it covers an access hole, possibly allowing you to skip adding an access panel. Keep in mind that replacing a faucet using this smaller hole can be difficult if not impossible—a large access panel makes the job much easier. You’ll find oversized cover plates (about $23) at plumbing supply stores or online (search for “renovation cover plate”).
To install a single-handle faucet, you’ll have to cut a hole into your shower surround. If your surround is fiberglass or acrylic, cut the hole using a jigsaw and a fine-tooth blade (a coarse blade causes more vibration, which can crack the surround). Apply strips of masking tape to the surround to avoid scratching or chipping the surface. Run the saw at full speed, but push it slowly and gently along the cut mark. If you feel the blade hitting a pipe inside the wall, stop immediately and continue past the pipe using a hacksaw blade.
To cut tile, use a rotary tool equipped with a tile-cutting bit (Photo 1). Set the cutting depth of the bit at 1/4 in. and make the first pass. Make more passes, setting the bit 1/4 in. deeper each time until you’ve cut completely through the surround. If you don’t own a rotary tool, you have a few other options: You can try a jigsaw and ceramic tile blade (about $5). These blades cut softer tile well. If you find that your tile is too hard, drill a series of 1/4-in. holes through the tile and wall using a carbide ceramic tile bit (about $5). Drill the holes close together so there’s little or no space between them. Then cut any material between the holes with the ceramic tile jigsaw bit.
Required Tools for this how to change shower fixtures project
Have the necessary tools for this DIY shower faucet replacement project lined up before you start—you’ll save time and frustration.
You’ll also need soldering supplies (solder, flux and emery cloth) and a rotary tool tile-cutting bit, a ceramic tile jigsaw blade and/or a ceramic tile drill bit.
Required Materials for this how to change shower fixtures project
Avoid last-minute shopping trips by having all your materials ready ahead of time. Here’s a list.