I know there's been a few posts on the filling. I fill mine to the top so that cap isn't floating and have never had a problem with that. I refill before there's just a drop - when I turn the eGo upside down and see some air in the tank above the fluid, I refill. .Also I might mention, that with the T's and C, I've never had a 'flooding' problem - something that occurs on every other system/carto/cart that I've tried.