Pressure-testing gas lines to find a leak is only half the job. if a pipe joint still leaks after using adequate thread sealant, here’s exactly what to do next to fix it properly and safely.

If a joint leaks despite correct thread sealant, first stop and depressurize the line, then dismantle the offending joint and inspect the threads under a bright light and magnifier; look for uneven, flattened, or burred threads that prevent metal-to-metal contact and cause sealant failure. Next, check for cross-threading by measuring thread engagement: threads should run full length without tight spots. if engagement is less than three full threads in a typical gas fitting or shows lateral gaps, replace the male and female parts rather than relying on more sealant. Examine the mating surfaces for nicks, dents, or cracks that propagate from over-tightening; a hairline crack can leak under pressure even with perfect thread tape. Feel the pipe ends for embedded debris or metal shavings from a poor cut. these can score the sealing surface and let gas bypass the sealant; re-cut the pipe squarely with a proper pipe cutter and deburr both inside and outside. If the fitting is made from soft metal, check for compression-ring deformation or crushed ferrules. replace the ferrule assembly and avoid using excessive torque; use a torque wrench and follow manufacturer torque charts to prevent deformation. When using tapered pipe threads, confirm you used the right thread sealant type. do not mix pastes intended for oxygen service or use general-purpose tapes that lack gas certification; use gas-rated joint compound or three-half wrap of gas-rated fluoropolymer tape applied in the direction of threading. If the leak source is a crack in the pipe or fitting, cut out the damaged section and install a new length with factory fittings or use a listed mechanical coupling rated for gas; never use plain compression fittings not rated for gas. Finally, after reassembly, perform a proper pressure test with a manometer or calibrated gauge at the required test pressure, and monitor for at least the code-prescribed duration while using a compliant leak-detection solution; document the results and label the repair with date and installer credentials.

One of the most common mistakes is relying solely on thread sealant instead of checking thread condition, which causes persistent gas line leaks. fix by disassembling, inspecting for damaged or mismatched threads, and replacing parts as needed; another frequent issue is over-tightening that strips or crushes threads and fittings, so use a torque wrench and follow manufacturer torque specs to avoid stress fractures; the third typical problem is using the wrong sealant or poor taping technique, leading to certification failures and slow leaks. always use gas-rated joint compound or recommended fluoropolymer tape applied correctly in the thread direction and verify compatibility with the fitting material.

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