Step 7 · Test for Leaks
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.