My shower arm broke off in the 1/2" pipe from the wall. How do I get the threaded piece out of the pipe? It broke off at the threads. Thank you.

You're looking for a tool like these to remove the broken shower arm.......the first one PROBABLY won't work because the elbow is too short to allow the extractor to enter far enough to engage.........

http://www.plumbingsupply.com/extractors.html

Normally I would suggest a 1/2" extractor sometimes called an easy out.

BUT they seldom work on broken threads in an elbow

So the next step is to use a hacksaw blade with very fine teeth and very slowly and carefully cut the thewads in two places NOT damaging the threads of the elbow inside the wall.

Then take a very sharp chisel of an old flat screw driver and gently tap the screw driver under the threads you cut (Between the two cuts) once you knock out this section of threads you can now bend the soft brass threads in and use a needle nose plyers to pull them out.

When making up the new shower arm use plenty of teflon IF you do damage the Ell threads then use QUICK WICK and lock or other quality joint compound to hopefully stop any leaks that may be caused by the damaged threads

I had this same problem. ez outs and internal pipe wrenches did not work for me. they kept stripping and wouldn't grab the broken threads. I wasn't very keen on using a hacksaw as another user suggested. what DID work for me was a 1/2" pipe tap. these are made to cut threads into unthreaded pipes. i just attached it to a socket wrench and went to town. it cut the broken threads right out and kept the female piece intact. this tool cost me about 20 bucks and saved me the cost of hiring someone to cut out my wall and replace the pipes inside it. USE THE PIPE TAP!! IT'S AWESOME!!!

Yup pipe taps work UNTIL you cross thread an existing female thread inside the wall or place to much force and snap a yellow brass thread inside the wall.

I ALSO HAVE HAD THE PROBLEM OF THE SHOWER ARM BREAKING OFF AT THE THREADS INSIDE OF THE IRON RISER PIPE. I TRIED MANY
OF THE SOLUTIONS I FOUND ON THE INTERNET WITHOUT SUCCESS.
WHILE SEARCHING FOR PIPE EXTRACTORS, I CAME ACROSS THE HARBOR FREIGHT TOOLS WEBSITE WHICH SELLS A DRILLMASTER PIPE NIPPLE EXTRACTOR SET, ITEM NUMBER 93822, FOR $5.99 PLUS SHIPPING. SINCE THERE IS A HARBOR FREIGHT TOOLS NEARBY, I WENT TO THE STORE AND PURCHASED THE TOOL FOR $7.99 PLUS TAX. IT WORKED LIKE A CHARM! IT IS A SET BUT YOU ONLY NEED THE 1/2 INCH EXTRACTOR FOR THIS JOB. USE A 3/4 INCH SOCKET AND YOU MAY HAVE TO ENLARGE THE HOLE IN THE GROUT BASE SLIGHTLY TO ACCEPT THE SOCKET. I ALSO USED A T-HANDLE IN ORDER TO APPLY THE TORQUE EVENLY. IT TOOK A BIT OF STRENGTH TO GET THE BROKEN PIECE STARTED, BUT ONCE STARTED IT CAME OUT WITHOUT DAMAGING THE IRON RISER PIPE THREADS.