The hand pump water supply is perfect for the user who has 1 or 2 vehicles, (golf car, pallet jack, etc.) and would like to use distilled water. To operate, simply connect the hand pump to your Pro-Fill system and place the other end in a gallon of distilled water. Begin to fill by squeezing the pump. When all of your batteries are filled, the bulb will become firm, not allowing you to add any more water. Simple & easy to use. Cost effective design. Built in line strainer.