A check valve that reduces leakage caused by flapping is disclosed. The shape of the heat seals focus the flow of gas in the valve so that the flapping that results from using elongated parallel heat seals is reduced. Alternative embodiments also enable tying of balloons while reducing the risk of leaking. Balloons can also be inflated at a greater rate without risk of leakage thereby reducing labor costs and the reduction in leaks also reduces the return of faulty products.