Which joint type is NOT listed as acceptable for gas piping?

Which joint type is NOT listed as acceptable for gas piping?

• A. Threaded
• B. Flanged
• C. Soldered
• D. Welded

Answer: (C)

Gas piping must use joints that provide a durable, leak-tight seal and are approved for fuel-gas service. Soldered joints are not considered acceptable for gas piping because they’re not deemed reliable enough to maintain a leak-tight seal under gas pressures and thermal cycling, and many codes restrict soldered joints for fuel gas (often due to potentially lead-containing solders and lower strength). Soldering is typically used for water piping, not for fuel gas systems. In contrast, threaded, flanged, and welded joints are standard, code-recognized methods for gas piping. Threaded joints use proper sealants to achieve a tight seal; flanged joints offer a robust seal and easy disassembly where needed; welded joints provide continuous, strong joints for steel piping and are routinely tested for leaks. For copper piping, brazed joints are commonly allowed, but ordinary soldered joints are not. That’s why soldered is the correct choice as the one not listed as acceptable.

Gas piping must use joints that provide a durable, leak-tight seal and are approved for fuel-gas service. Soldered joints are not considered acceptable for gas piping because they’re not deemed reliable enough to maintain a leak-tight seal under gas pressures and thermal cycling, and many codes restrict soldered joints for fuel gas (often due to potentially lead-containing solders and lower strength). Soldering is typically used for water piping, not for fuel gas systems.

In contrast, threaded, flanged, and welded joints are standard, code-recognized methods for gas piping. Threaded joints use proper sealants to achieve a tight seal; flanged joints offer a robust seal and easy disassembly where needed; welded joints provide continuous, strong joints for steel piping and are routinely tested for leaks. For copper piping, brazed joints are commonly allowed, but ordinary soldered joints are not. That’s why soldered is the correct choice as the one not listed as acceptable.