To avoid having to fix a leaking shower arm it is always a good idea to use pliers to hold against the pressure while unscrewing a shower head. There is normally no way to hold against the pressure when unscrewing a shower arm so try some lubrication like WD-40 if it doesn’t loosen easily.
To fix a leaking shower arm is usually a more involved project but it can be done with some patience.
To fix a leaking shower arm caused by a broken pipe in the wall:
- The first thing to do is to expose the broken pipe. Measure the location of the shower head from the wall and from the ceiling. Transfer the measurements to the wall directly behind the shower and mark it with an x. Then draw out a square that will give you enough room to work to make the repair. Cut the drywall out. It is important to take your time and cut the drywall in a nice square or rectangle so that you can put the piece back in and make a clean wall repair after the plumbing repair is complete.
- With the pipe exposed determine what you will have to do to repair the broken pipe. If the the cause of the leak is a copper pipe that was split when the shower arm was twisted too far then the copper pipe will have to be cut out to get a good piece of copper. Then the pipe can be put back with a coupling, some extra pipe, and a new sweat by threaded elbow.
If the cause of the leak is at a joint you may only need to repair that coupling joint to repair the leak.
- Make a list and run to the hardware or home improvement store to get what you need. It may be helpful to take a picture with your smartphone for reference or in case you need some advice while shopping. There is usually more that one way to make a repair so keep an open mind and explore the options that you are most comfortable with. There are push on fittings that could be used to complete the repair without soldering if you prefer.
- Cut the copper pipe below the break using a pipe cutter. Measure the old pipe to find the necessary length for the new piece of copper pipe. Clean the ends of the copper pipe with sand cloth and then push the pieces together to see how they fit. Make any necessary adjustments. Apply flux to both sides of each fitting and to the ends of the pipe. Get it all into place and screw the shower arm loosely into the wall and make sure it is perfectly straight before soldering. Carefully solder all of the joints making sure to go all the way around and to not to miss any.
- Once the soldering is complete you can screw the shower arm and flange into place after applying Teflon tape. Then screw the shower head onto the shower arm with Teflon tape. Turn the water on to the shower and check behind the wall for leaks. You may want to leave the wall open for a few days to air out the web surfaces and to make sure there are no leaks before repair the drywall. Or you can install an access panel in the wall for future access or for a quick fix.