• 1). Close the main water valve in your home.
  
  
• 2). Turn on your shower. Doing this will empty all the water in the pipes, so when you remove the brass valve inside the wall, there will not be much water leakage.
  
  
• 3). Loosen the unions on each side of the brass valve holding it in place; there should be four total. A union is a large brass fitting with a nut on the middle of it and lets you connect to stationary pipes together. A plumber's wrench will be needed to loosen the nuts.
  
  
• 4). Remove the brass valve out of the wall after you have unscrewed the four unions.
  
  
• 5). Unscrew the pieces of copper pipe that are threaded into the brass valve and are also connected to the other halves of the unions.
  
  

Installation

• 1). Screw the pieces of copper pipe that you just removed from the old brass valve into your new valve.
  
  
• 2). Replace the valve back in the wall, threading all of the unions back together. You may need to use a plumber's wrench to tighten the unions' nuts.
  
  
• 3). Open the main water valve in your home.