What a shower arm and flange are, and why they fail
The shower arm is the pipe that sticks out of your wall and holds the showerhead. The flange is the trim ring that sits flat against the wall where the arm comes through—it hides the hole and seals the gap. Together they're one assembly, and when water leaks behind the wall or the arm corrodes, you replace both as a unit.
The arm fails because water gets trapped inside it or behind the flange. Corrosion eats through the metal from the inside out, or the sealant around the flange dries and cracks, letting water into the wall cavity. Once that happens, the arm becomes brittle and can snap, or the connection inside the wall loosens. Replacing the arm and flange stops the leak and prevents rot in the framing behind your wall.
This is a job you can do yourself if you're comfortable with basic plumbing and have access to the wall from behind—either from a basement, crawlspace, or attic. If your shower is on an exterior wall or you can't reach the back, call a plumber. If the wall is already soft or discolored, water damage may have spread and you'll need a professional to assess the framing.
Key Takeaways
- You will need to access the pipe from behind the wall, either through a basement, crawlspace, or the other side of the wall in an adjacent room.
- The arm screws into a fitting called a drop ell inside the wall; you unscrew the old arm, unscrew the old flange from the wall, then install the new flange and arm in reverse order.
- Use plumber's tape (also called thread seal tape or PTFE tape) on the threads where the arm screws in to prevent leaks.
- Caulk around the flange with silicone caulk after installation to seal the gap between the flange and wall and prevent water from running behind it.
- If the drop ell inside the wall is corroded or leaking, you will need to replace that too, which requires soldering or unthreading it—this is when to call a plumber.
Tools and materials you'll need
Gather these before you start: an adjustable wrench or pipe wrench, a screwdriver (usually Phillips head, sometimes flathead), plumber's tape, a new shower arm and flange kit (buy the whole assembly—don't mix old and new parts), silicone caulk, a caulk gun, a utility knife, and a rag or old towel.
If the old arm is stuck or corroded, you may also need penetrating oil (like WD-40) and a wire brush. Have a bucket or pan ready in case water drips from the pipe inside the wall. If you're replacing the drop ell as well, you'll need a soldering torch and solder, or you'll need a plumber—don't attempt this without experience.
How to access the pipe from behind the wall
The first step is finding where the shower arm connects inside the wall. If your shower is on an interior wall, you may be able to access it from the other side—through a closet, hallway, or basement. If it's on an exterior wall, you'll need access from the attic or crawlspace above, or from the basement below, depending on your home's layout.
Once you're in the space behind the wall, locate the drop ell—the fitting the arm screws into. It will be near the back of where the showerhead sticks out. Shine a flashlight and trace the pipe. If you can't find it, drill a small pilot hole through the wall from the shower side (in an inconspicuous spot) to help you locate it from behind. You'll patch this hole later.
Clear away any insulation or debris around the fitting so you have room to work. If there's water pooled or the wood is soft, stop and call a plumber—the damage may be worse than just the arm.
Removing the old arm and flange
From inside the wall, use your wrench to unscrew the shower arm from the drop ell. Turn counterclockwise. If it's stuck, spray penetrating oil on the threads, wait 15 minutes, and try again. Once the arm is loose, unscrew it by hand and set it aside. Water may drip—have your bucket ready.
From the shower side, use a screwdriver to pry the old flange away from the wall. It's usually held by caulk and sometimes by small screws or nails. Work slowly so you don't damage the wall. Once the flange is off, scrape away all the old caulk and debris with a utility knife or putty knife. The wall surface should be clean and dry before you install the new flange.
Installing the new flange and arm
Start from the shower side. Position the new flange against the wall so the hole lines up with where the arm will come through. The flange should sit flat. If the wall is uneven, you may need to shim it with thin plastic shims so it doesn't rock. Once it's positioned, mark the screw holes (if your flange has them) and drill pilot holes. Screw the flange in place, but don't fully tighten yet—you'll adjust it once the arm is in.
From inside the wall, wrap the threads of the new shower arm with plumber's tape. Wrap it clockwise, overlapping each turn slightly, and wrap it around three to four times. This creates a watertight seal. Screw the arm into the drop ell by hand first, then use your wrench to tighten it firmly—but don't over-tighten, which can crack the fitting. The arm should be straight and level.
Go back to the shower side and tighten the flange screws fully. The flange should be snug against the wall with no gaps. If the wall is slightly uneven, the flange may rock a little—that's normal, but it shouldn't move when you push on it.
Sealing the flange to prevent future leaks
This step is critical. Run a bead of silicone caulk around the entire perimeter where the flange meets the wall. Use a caulk gun and explore steady, even pressure. The caulk should fill any gap between the flange and the wall surface. Smooth it with a wet finger or caulk tool so it's flush and looks finished.
Let the caulk cure for the time listed on the tube—usually 24 to 48 hours—before you use the shower. Don't paint over it; silicone caulk is meant to stay visible and flexible so it can move with the wall and the flange without cracking.
If you drilled a pilot hole to locate the drop ell, patch it from the shower side with a small piece of drywall or a wall patch kit, then caulk and paint to match.
When to call a plumber instead
Call a professional if the drop ell itself is corroded, leaking, or stuck and won't unscrew. Replacing a drop ell requires soldering (if it's copper) or unthreading it (if it's threaded), and both are jobs that need experience to do without damaging the pipe or creating a worse leak.
Also call a plumber if you can't access the pipe from behind the wall, if the wall is soft or water-damaged, or if you find mold or rot in the framing. These signs mean the leak has been there a while and the damage may be extensive.
Frequently Asked Questions
Can I replace just the flange without replacing the arm?
No. The arm and flange are sold as a matched set, and the arm threads are designed to work with the specific flange. Mixing old and new parts often leads to leaks. Buy the complete assembly and replace both.
What if water is still dripping after I tighten the arm?
The leak is likely coming from inside the wall at the drop ell connection, not from the arm itself. Check that you wrapped the threads with plumber's tape and tightened the arm firmly. If it still drips, the drop ell may be damaged and needs to be replaced by a plumber.
Do I need to solder the new arm in place?
No. Shower arms screw into the drop ell using threads and plumber's tape—no soldering required. If your drop ell is soldered to the main supply line, you don't touch that. You only unscrew and rescrew the arm itself.
How long does this job take?
If you have straightforward access to the pipe from behind the wall and the old arm isn't stuck, plan on one to two hours. If the arm is corroded and you need to soak it with penetrating oil, add another 30 minutes. Caulk cure time is separate and happens while you're not working.
What's the difference between plumber's tape and regular tape?
Plumber's tape (PTFE or thread seal tape) is thin, slippery, and designed to fill microscopic gaps in pipe threads without hardening. Regular tape is thicker and sticky. Always use plumber's tape for this job—it's inexpensive and prevents leaks far better than anything else.