Skip, lack of penetration is not allowed, although this code states that:136.4.5(A.5) root concavity when there is an abrupt change in density, as indicated in the radiograph. Which means if a suck back or a lower spot in a root bead does not show up darker than the parent metal on the RT it is acceptable. With a visual test this is a judgement call by the inspector, visual criteria doesn`t allow any incomplete penetration. Unlike B31.3, B31.1 is unforgiving even on a water line. It`s like they say weld them all the same and "make`em all shoot".... Good Luck and Have a good one!