How to Convert a 3-Handle Shower Faucet to a Single-Handle Valve

The first and most critical step is to ensure the water supply is completely turned off to prevent flooding. Locate the main water shut-off valve for your house, which is typically found in the basement, a crawl space, or near the water meter. Turn the valve clockwise until it stops. Then, open faucets at the highest and lowest points in your house to relieve pressure and drain the remaining water from the pipes. Place a bucket inside the tub or shower stall to catch any residual water that will drip out when you begin disassembling the old faucet.

First, remove the old faucet trim. This includes unscrewing the three handles and the escutcheon plates behind them. You may need a Phillips head or flathead screwdriver and possibly an Allen wrench. The tub spout might unscrew or have a set screw on the underside. Next, you must create an opening in the wall large enough to access and work on the valve body and pipes. For a tiled wall, use a grout removal tool to score the grout lines in a rectangular shape around the three valves. Then, use an angle grinder with a diamond blade or an oscillating multi-tool with a tile blade to carefully cut the tile and backer board along the scored lines. The opening should be large enough to comfortably fit your hands and tools, typically around 12 inches wide by 10 inches high. Wear safety glasses and a dust mask.

With the valve exposed, you need to disconnect it from the house plumbing. You will see the hot and cold water supply lines connected to the bottom of the two outer valves, and two pipes coming from the central diverter valve: one going up to the shower head (shower riser) and one going down to the tub spout. Using a mini tubing cutter, cut the hot and cold copper pipes below the valve body. Then, cut the shower riser pipe above the valve body and the tub spout pipe below it. Once all four pipes are cut, the old valve assembly can be removed from the wall cavity. It may be screwed to a wood brace; if so, remove those screws.

Now you must re-route the plumbing to fit the new single-handle valve. This is the most complex part. You will need to use new sections of copper pipe and various fittings (like 90-degree elbows) to bring the hot and cold lines from their original wide positions to the narrow inputs on the new valve. Use a tape measure to determine the lengths of pipe needed. Dry-fit all your new pipe pieces and fittings first to ensure everything lines up correctly. The new valve must also be mounted securely to a new wood brace (e.g., a 2x4) placed between the wall studs. Crucially, you must follow the manufacturer's instructions for the valve's 'setback'—the distance from the front of the valve to the front of the finished wall. A plastic depth guard is often included with the new valve for this purpose.

Once everything is dry-fitted, disassemble the connections. Thoroughly clean the outside of the pipe ends and the inside of the fittings using a pipe cleaning brush and emery cloth until the copper is shiny. Apply a thin layer of water-soluble flux to all surfaces to be joined. Reassemble the pipes and fittings. Using a propane or MAPP gas torch, heat the joint evenly. When the flux sizzles, touch the lead-free solder to the opposite side of the joint from the flame. The heat will draw the solder into the joint, creating a seal. You will see a silver ring appear when the joint is full. Repeat for all connections: hot in, cold in, shower riser out, and tub spout out. Use a flame shield to protect the wood framing from the torch flame. Make sure the valve's cartridge is removed before soldering, as the heat can damage it.

This is a moment of truth. Re-install the valve cartridge that you removed before soldering. Ensure the test cap that came with the valve is securely installed on the valve body. Slowly and carefully, turn the main water supply back on. Return to the shower and meticulously inspect every single soldered joint for any signs of dripping or moisture. Use a dry paper towel to wipe each joint, which will make even the smallest drop of water visible. Check the hot, cold, shower riser, and tub spout connections. If you find any leaks, you must shut off the water, drain the system, and re-solder the leaking joint.

Once you are 100% certain there are no leaks, you can repair the wall. You cannot simply re-install the tile you removed, as the new faucet trim (escutcheon) is much smaller than the hole. This is where a 'Remodel Plate' (also called a 'Goof Plate' or 'Smitty Plate') is essential. It's a thin piece of stainless steel or plastic that is larger than your hole but smaller than the new decorative escutcheon will cover. You will install a new piece of moisture-resistant drywall or cement board to patch the majority of the hole, leaving an opening for the valve. Then, apply a waterproof membrane over the patch. The remodel plate is then installed over this, providing a solid, flat surface. Finally, you can tile over the patch and plate, or if using a very large plate, seal it directly to the surrounding tile with 100% silicone caulk.

With the wall repaired and sealed, you can install the final trim pieces. Remove the test cap and plastic depth guard from the valve. Slide the trim sleeve (if included) over the valve body, followed by the large decorative escutcheon plate. Seal the top and sides of the escutcheon with a bead of silicone caulk, but leave a small gap at the very bottom to allow any water that gets behind it to escape. Attach the handle according to the manufacturer's instructions; this usually involves a small set screw. Finally, screw on the new shower head (use Teflon tape on the threads of the shower arm) and install the new tub spout. If it's a slip-on type, slide it on and tighten the set screw. If it's a screw-on type, apply Teflon tape to the pipe threads and screw it on tightly. Turn the water on and test the function of the handle, diverter, shower head, and tub spout.