It's very easy to fill your WaterPORT with your garden hose. It fills quickly and gets to the correct P.S.I. automatically. But sometimes you aren't at home! Sure, you can re-pressurize your tank with a bike pump, but what if you don't want to carry one round? Enter the Pump Cap! This handy accessory replaces the stock fill cap on your Day Tank and allows you to easily add pressure when on the road. Less than 30 seconds of pumping will bring your tank up to the optimal P.S.I. and have you cleaning, showering, spraying, or doing whatever needs to be done with the Day Tank. Please note that the Pump Cap will not work on the first generation of WaterPORT tanks. It only works on the Day Tank version of that size. The Pump Cap does also work on the Weekender tank, and it comes included with the GoSpout tank.