All these Kangertech atomizers have got airflow vents at the bottom of the tank and the juice (e-liquid) could flow out after filling the tank and closing its cap or if you put the mod away with fresh juice filled in tank. This could be real frustrating since you won’t be able to carry the vaporizer with you due to the fear of juice leaking into your pocket.
Kangertech Subtank, Protank or Toptank leaks due to the pressure building up in tank after filling and closing the cap (mouth piece). When you screw down the mouth piece the air in tank push the liquid, floods the coil and it may start leaking through air flow vents.
Before filling tank, close the juice flow holes (see image below for illustration). Fill the tank. put the cap back and screw it down very slowly. Open these holes to let the juice flow if you are not able to vape and close them back right after few seconds. Usually these holes in chimney are not air tight. So if juice is not too thick due to the higher concentration of VG (vegetable glycerin), it will start flowing on its own without even opening them.
While filling and closing the tank if coil gets flooded for any reason, blow air into the atomizer 3 or 4 times and this will clear excessive liquid from the coil. You may put a tissue paper around the air vents to stop liquid drops flowing down the MOD when you blow into the atomizer.