PEX piping has revolutionized residential plumbing. It is flexible, affordable, resistant to freezing, and much faster to install than traditional copper. For water supply lines running through walls and under floors, PEX is an excellent choice. But there is one place it should never be used: connecting directly to a tub spout. This might seem like a minor detail, but using PEX for a tub spout connection can cause real problems.
The primary issue is structural support. A tub spout needs a rigid, stable connection to the wall. Copper pipe — the correct material for this application — threads or slips directly into the spout and is soldered or secured firmly in place, creating a solid connection that does not flex or move. PEX, by contrast, is inherently flexible. When you push or pull on a tub spout connected with PEX, the pipe gives. Over time, this movement loosens the connection, causing leaks behind the wall.
The diverter mechanism in many tub spouts adds to the problem. When you pull the diverter knob to redirect water from the tub spout to the showerhead, you create back-pressure in the spout connection. A rigid copper stub-out handles this pressure without issue. A flexible PEX connection can flex under pressure, stressing the fitting and accelerating wear. The result is a connection that fails sooner than it should.
Another concern is the type of fitting required. Tub spouts are designed to connect to either a threaded or slip-on copper stub-out. While adapters exist to connect PEX to tub spouts, they add complexity, additional failure points, and often do not meet manufacturer specifications. If the tub spout fails and you file a warranty claim, the manufacturer may deny the claim if the spout was installed on PEX rather than the specified copper connection.
The correct approach is simple: run PEX to the wall cavity, then transition to a short copper stub-out — typically 6 to 8 inches of copper pipe — that extends through the wall for the tub spout connection. This gives you the benefits of PEX for the supply run while providing the rigid, stable connection the spout requires. Any qualified plumber knows this, but it is a shortcut that less experienced installers or DIY enthusiasts sometimes take.
At EZ Bath, we pay attention to details like this because they determine whether your bathtub remodel holds up over time. Proper plumbing connections, correct materials, and professional installation techniques are what separate a quality remodel from one that causes problems down the road. Contact us if you have questions about your bathroom plumbing or if you are planning a remodel.
