Bathmate Hydromax Penis Pump. The Hydromax Series (formerly Hydromax X-series) is the next stage of Hydro Pump evolution. Developing the innovative Bathmate, the new bellows pump and valve give 35% more power than the original Hydro7 with more safety and comfort. The most important change, and certainly the most technically challenging, is the engineering of a new valve that controls the flow of water out of the device. By adding a new latch (or switch) to the valve you can now close the valve to prevent water escaping when filling. This small but important change now allows you to fill the device with only one hand leaving the other free to sort yourself out or get your accessories ready.