So there's a new Hydration System on the market. One of the most unique we have seen yet. It is a pressurized system with many add ons. Not only can you add air pressure to an external pocket of the bladder, they made the engine (bladder) fit in your standard hydration carrier. We would recommend taking the time to look at GreigerRig though as they put a lot of effort into the design of their own packs. They also made the engine dishwasher safe. When you want to clean it you simply turn it inside out and put it on the top shelf of your dishwasher. A huge bonus to the GeigerRig is the quick connect inline filter. It doesn't need to be gravity fed due to the fact that the engine is pressurized.