If it's wicked right it shouldn't leak at all. The one thing that gets them is pressure changes. The juice is balanced in the tank by pressure differential. If ambient pressure lowers quickly-- they're famous for leaking on airplanes-- the pressure in the tank will force juice through the wick into the coil area and it will run out the air holes. That, however, isn't about RTAs. Premade coil tanks do it too. If that worries you, it can be beaten: don't fill the tank completely full, and store it upside down. This will run all the juice to the top of the tank, leaving the wick holes in the air bubble above the juice. It won't leak at all like that as there is no juice by the wick to get forced through. The only other problem is filling, but there's a technique that works on that, too. One caveat: Genesis style tanks are famous for leaking when laid down. They work differently, but the MT is not that kind of tank. I store my MT on its side overnight every day. I fill it after I come home from work, fresh battery in the mod, etc., then zip it up in the pouch and lay it with my day book ready to go in the morning. It doesn't leak like that.