Reasons why electronic cigarette(ecig) tanks leak. The majority of leaks are due to excess juice within the airflow chamber and/or coil. Other leaks can be caused by missing or damaged o-rings, insufficient wick material(commonly cotton), broken glass, loose or overly tight connections. I intend to describe several of the reasons for internal leaking caused by excess accumulated juice and temperature related leaking. Excess accumulated juice: I need to explain some basics in-case my audience includes some noobs(no offense). Normally when someone uses an ecig the fire button is pushed about the same moment the juice junkie inhales a massive lung hit drawing tons of fresh air thru the intake vents into the airflow chamber where it is mixed with the vaporizing liquid which is now a juicy mixture of food flavoring, nicotine and food preservation products (I was going to say antifreeze but I will leave that to the ignorant and government officials(offense intended).). After leaving the coil the tasty mixture travels upward for some distance in what I call the “airflow chamber” and mouthpiece. This is where one problem occurs. The longer or taller your tank is the more surface area the vapor passes by. The more surface area the vapor passes the more juice accumulates on the walls in the tank. Leaking occurs because the accumulated juice pools together in droplets and follows the path of least resistance downward and onto your hand, fingers, floor, shirt, pants and anywhere else it can. And here is the solution, all you need to do is let go of the fire button a second or two BEFORE you stop inhaling. What your doing is inhaling all the vapor that would have otherwise been left to stick to the side of the airflow chamber and coil. That's it, it's that easy. By making this standard practice you will eliminate most of your leaking. Try it! Temperature related leaking: Leaking related to temperature has several causes. The most important temperature related cause is that eliquid becomes “thinner”(viscosity) as it's temperature rises. Add this to the problems below and you have a mess. Temperature has a lot to do with leaks especially when you are filling or have recently filled a tank. Normally after an awesome vaping session and while the tank is still hot(important) the lid is removed and cool juice is poured into the hot and empty tank and the lid is securely replaced. What you have just done is created a mini pressure cooker. As the new cool juice is being warmed from the hot internal tank parts(glass,base and any remaining juice) the expansion pushes the juice thru the cotton into the airflow chamber where there is little chance excess juice will be vaporized. Because e-liquids expand when the temperature increases the temperature of the tank and it's parts should be at room temperature when filling. And a good tip for chain vapors. If you cannot put your tank down long enough to let it cool before it's filled try using two tanks and cycle them. What also occurs is like a can of beer were a drinker cuts a hole in the bottom of the can, turns it up and pulls the top allowing air to rush in and beer to flow out. The longer you have the lid off the tank the more excess juice will seep thru the cotton and into the airflow chamber. Excessive juice that cannot be vaporized by the coil will leak out of the tank. Also, using an almost pure vegetable glycerin(VG) solution can help to reduce leaking. VG has a thicker consistency then PG(propylene glycol) which makes ejuice mixtures containing a higher level of VG less susceptible to leaking. It will not stop leaks it's just that PG leaks more then VG. I use an 80/20(VG/PG) mixture and still have leaking issues daily. Another tip is to keep your ejuice mixtures in the freezer or refrigerator so they maintain their thickness longer(just until it's warmed back up).