There are a number of common defects which violate welding quality specifications. The most common of these defects are slight inclusions caused by inexperienced use of welding equipment by novice welders. Slight inclusions can also be a symptom of attempting to weld in an awkward workspace that impedes the manual dexterity of the welder.

Another common defect is the inclusion of gas pores within the weld filler material; this defect can be caused by either moisture on the welder's electrodes or impurities on the pipe groove surface. To prevent gas pore inclusion, store electrodes in a dry container and clean the pipe edges before beginning the weld. Gas inclusion can also indicate improper tool use such as welding on a low power setting. Cracks can form within the pipe's edge material due to moisture inclusions or welding on to low an energy arc setting.

Other defects, such as incomplete penetration and undercut defects, are results of welder technique error and can be offset by additional practice and consulting textbook materials for proper techniques.