Sprayers should be completely emptied and rinsed with water after each use to prevent corrosion from any chemicals left in the tank or hose. It usually takes at least a gallon of water to fully clean the tank, but it might take more depending on the chemicals and tank size. Gas-powered pumps take more maintenance because they need winterizing with antifreeze during cold months. If the sprayer has been sitting for a while, be sure to check and lubricate the O-rings and seals before using it.