Hi, thanks for your question. I see what I think you mean is the thin black lines on that first pic. I'm looking at the pipe now and covering the bowl and blowing into the stem I do not feel any air coming from that area so if it is a crack it is superficial and not all the way through. When I run my fingernail over it I do not feel a crevice, it is smooth so may just be a cosmetic defect. Hope that helps.