I installed a nipple in a water bottle for my brooder and it leaked. I would have sworn up and down it was coming from the nipple, but I put some silicone around the outside and it stopped leaking. Recently I made a PVC waterer though and one of he nipples in that kept leaking. I reinstalled it to make sure it was pointing straight down, but no difference. I ended up replacing just that nipple and it's fine now. For the record, I have 4 in my PVC waterer, used an 11/32 drill bit, and used a drill to get them in (and I had to push on them a bit and clamp the drill around them too) and 3 of 4 were fine (well, 4 of 5 technically since I installed a different one). I did put silicone around them just in case, but they didn't leak without that either.