The water is the key. When I first got the expert drum and the foot pump I didn't know to fill it with water. It usually startled me as the lid exploded off the tank. So I started opening it by tapping the lid on a 2x4 to gradually push it up. Sometime later I read about the water trick, which has never failed to gently open the tank. However I do it a bit differently than the video in that I fill it right up to the top. You need to open it in a sink this way, but it's much gentler on the tanks.