I've found that if you don't get the wicking right for the smok TFV4 it'll leak like crazy. When wicking it try to avoid putting the cotton down through the "wick holes" on the bottom of the deck. Unless you get it perfectly set in there it'll get bound up in the threads and leak down through to the air holes. If u just fan the cotton up like pancaking around and up higher than where the thing threads into the bottom of the deck it seems to work pretty well. Although I've found it will still leak if the tank is filled to full. I try to fill it to a little over half full, near the top of the rta chimney, and I haven't had any leaks doing it that way. Good luck.