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

Begin by ensuring a safe and clean work environment. Locate the main water shut-off valve for your house and turn it completely off. To drain the remaining water from the system, open the faucet you are working on, as well as a faucet on a lower floor (like a basement sink). Place a protective drop cloth over the tub or shower floor to prevent scratches and to catch debris. Have a bucket ready to catch any residual water from the pipes.

Carefully remove the existing faucet trim. This includes the hot handle, cold handle, and the central diverter handle. These are typically held on by a small set screw (requiring an Allen wrench) or a Phillips head screw hidden under a decorative cap. Once the handles are off, unscrew the surrounding trim plates, called escutcheons. Finally, unscrew the tub spout; you may need a strap wrench or pliers (with the jaws wrapped in tape to prevent scratching the finish) if it's tight.

To access the plumbing, you will need to cut an opening in the wall. First, use a stud finder to locate the studs on either side of the existing plumbing. Mark the area you need to cut. The opening should be large enough to comfortably work on the plumbing and will be centered on the valves. For a tiled wall, use an angle grinder with a diamond blade to carefully cut through the tile and grout along your marked lines. Then, switch to an oscillating multi-tool or drywall saw to cut through the drywall or cement board behind the tile. Be extremely careful not to cut too deep and damage any pipes or electrical wires inside the wall.

With the old valve assembly exposed, identify the hot and cold water supply lines and the shower riser pipe leading to the shower head. Using a tubing cutter, make clean, square cuts on these three pipes to disconnect the old valve body. A mini-tubing cutter may be necessary for pipes in tight spaces. Once the pipes are cut, carefully maneuver the old valve assembly out of the wall cavity.

Prepare the cut ends of the existing copper pipes for the new valve. Use a deburring tool to smooth the inside and outside edges of the cut pipes. Then, use sand cloth or emery cloth to thoroughly clean the outside of the pipes until they are shiny. This is crucial for a good solder joint. Next, prepare a mounting support for the new valve. Cut a piece of 2x4 lumber to fit snugly between the wall studs. Secure this wood block in place with screws, positioned so the new valve will be at the correct height and depth as specified by the manufacturer's instructions.

This is the most critical step. First, remove the plastic cartridge from the new valve body to protect it from the heat of soldering. Secure the new single-handle valve to the 2x4 wood block. Dry-fit all the necessary 1/2 inch copper pipe pieces and fittings (like elbows and couplings) to connect the hot inlet, cold inlet, and shower riser outlet of the new valve to the existing pipes. The bottom outlet for the tub spout must be capped with a 1/2 inch copper cap, as single-handle valves typically use the same outlet for both tub and shower, controlled by the diverter on the tub spout. Once everything fits perfectly, disassemble, apply a thin layer of flux to all pipe ends and inside all fittings. Reassemble and use a propane torch to heat each joint, applying lead-free solder until it flows completely around the joint. Use a flame shield behind the pipes to protect the wood stud and block.

Before closing the wall, you must test your work for leaks. Re-install the valve cartridge that you removed earlier. Go back to the main water shut-off and turn it on very slowly to allow the pipes to fill without causing water hammer. Return to the shower and carefully inspect every solder joint with a flashlight and a dry paper towel. Look for even the smallest drips. If a leak is found, you will need to shut the water off, drain the system, and re-solder the faulty joint.

Once you have confirmed there are no leaks, you can close up the wall. The simplest method is to use a remodel plate or cover plate. These are specifically designed to cover the large opening and the old handle holes, providing a clean, finished look. Place the foam gasket (if included) on the back of the remodel plate, position it over the opening, ensuring the hole for the new valve stem aligns correctly. Secure the plate to the wall or to the wood blocking using the provided screws. Apply a bead of 100% silicone caulk around the entire perimeter of the plate to create a waterproof seal against the tile wall.

The final step is to install the new faucet's decorative trim. Slide the escutcheon plate over the valve stem and secure it to the valve body or remodel plate with screws. Install the handle onto the valve stem, securing it with its set screw. Next, wrap the threads of the shower arm with plumber's tape and screw it into the fitting in the wall. Attach the new shower head to the arm. Finally, apply plumber's tape to the threads of the tub spout pipe nipple and screw on the new tub spout. Turn on the water and test the function of the handle and the diverter on the tub spout.