ASK & ANSWER FOR Taurus INDUSTRIAL CO.,LTD http://www.flangeun.com/faq/tags/visible-line.html 2013-12-12T03:27:45+00:00 Joomla! - Open Source Content Management Are pipe fittings having a visible line in them, are cracked? 2013-04-08T12:14:52+00:00 2013-04-08T12:14:52+00:00 http://www.flangeun.com/faq/are-pipe-fittings-having-a-visible-line-in-them,-are-cracked.html Jocelyn Kuke No. The noticeable line is not a crack. This you can test by trying to open the crack. If you are unable to open it up by pulling on the part then that is knit-line which is an intrinsic part of the injection-molding process. A knit-line will not impact the integrity of the pipe fitting. No. The noticeable line is not a crack. This you can test by trying to open the crack. If you are unable to open it up by pulling on the part then that is knit-line which is an intrinsic part of the injection-molding process. A knit-line will not impact the integrity of the pipe fitting.