Flare fittings are available for connecting lengths of copper tubing and adapting to iron pipe thread; the same fittings can also be used for which material of the same dimensions?

• A. Copper tubing
• B. Iron pipe thread
• C. Aluminum pipe
• D. Plastic pipe

Answer: (D)

Flare fittings are sized by the outside diameter of the pipe or tube they’re designed to seal against, not by the material. The fittings that connect copper tubing and that adapt to iron pipe threads are built around that specific outside diameter. If another material has the same outer diameter as the copper size being used, the same flare fittings can be used with it as well. Plastic pipe often comes in tubing sizes that match those outside diameters, so the same fittings can be employed for plastic pipe of the same dimensions. Aluminum pipe, even if it looks similar, usually doesn’t share those exact dimensions at the common sizes, so it isn’t automatically interchangeable.