According to a feature of {TAIL ~ the invention}, the tank has a number of water outlets spaced along {HEAD ~ the lower water collection region} and controlled by valves which may be programmed to open periodically and sequentially 
According to a feature of { TAIL ~ the invention } , the tank has a number of water outlets spaced along { HEAD ~ the lower water collection region } and controlled by valves which may be programmed to open periodically and sequentially
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