Step 5 · Solder and Install New Valve
Prepare the existing pipe ends by cleaning them inside and out with emery cloth until they are shiny. Dry-fit the new shower valve, using copper couplings to connect it to the existing pipes. You may need to cut small pieces of copper pipe to bridge any gaps. Once you have a perfect fit, disassemble it. Apply a thin layer of flux to the outside of the pipes and the inside of the couplings and valve fittings. Reassemble the pieces. Place a fire-resistant cloth behind the work area to protect the wood studs. Using a propane torch, heat the fittings (not the pipe) evenly. When the flux sizzles, touch the lead-free solder to the joint. The heat will draw the solder in, creating a solid seal. Repeat for all joints. Finally, secure the new valve to the stringer with screws, ensuring it is at the correct depth according to the manufacturer's instructions.