Abstract: A ball valve is provided with an internal check valve which is of modular construction and with an external valve casing that includes a lateral extension defining an access port. The modular check valve assembly is threadably connected to the ball and the lateral extension is closed with a threadable closure. The threadable closure for the lateral extension and the threadable check valve assembly both have sockets to receive access tools and both sockets preferably have the same unique tamper proof configuration to receive the same access tool.