Which of the following is a common pipe groove combination used in GTAW root passes?

• A. V-groove only
• B. V-groove, U groove, and J groove
• C. U-groove only
• D. J-groove only

Answer: (B)

When welding a pipe joint with GTAW, the root pass needs a geometry that allows the molten metal to fuse with the root properly while controlling heat input and finishing the root cleanly. Different groove shapes affect how easily the root is filled and how the bead sits at the root, so welders choose the groove profile based on wall thickness and fit-up.

V-grooves give a clear, open root opening that helps penetration and is common for thinner to mid-thickness pipes. U-grooves have a rounded bottom that can reduce the risk of undercut and help control reinforcement on thicker joints. J-grooves introduce a small landing or lip that can guide filler metal and help align and complete the root pass smoothly.

Because pipe joints come in a variety of thicknesses and bevels, a common practice is to use any of these groove types for root passes, depending on the specific joint. That flexibility is why all three—V-groove, U groove, and J groove—are listed as common options for GTAW root passes.