Protanks need a vacuum in the tank to keep from leaking. Running it too hot - chain
vaping - can heat it up and increase the pressure inside the tank. Any o-ring not sealing will cause no vacuum in the tank, then gravity takes over. Knockoffs leak, especially knockoff heads, and there's a lot out there. Make sure its a genuine Kanger. When not in use store upside down. They recommend keeping it over 1/3 full, but I vape my PT's down to practically dry at times and they have never leaked. Maybe I'm just lucky.