Water eliminators absorb water out of petroleum products. Simply drop the unit into your tank bottom, secure the chain to the fill cap or other convenient place. The crystals in the unit will swell when absorbing water in the tank. The water eliminator will have reached full capacity when the water retaining crystals have filled the entire unit. The chain facilitates easy removal of the saturated eliminator, leaving you with dry fuel. The WE-S31 Water Eliminator is 31" (790 mm) long, made of stainless steel and includes a stainless steel chain. It uses a replaceable fabric insert containing the water aborbing crystals. Each insert absorbs 1 gallon (3.8 liters) of water.