It's a sharpie mark. I temporarily used some plumber's tape, and this weekend I will finally have time to turn the pumps off long enough to silicone that leak.Is that union cracked or is that a mark leftover from a sharpie? Short of cutting it out you could undo the union put a shop vacuum up to the pipe and suck in some pvc glue into the joint. I have done this with success before when I really didn’t want to redo a section of pipe. Put your hand or a towel over the other end of that pipe to force the glue to get sucked in