We picked up a few of these:
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And affixed them in the bottom of a bucket. The bucket is filled with water and suspended over the chickens. Using this method, we don't have to fill their water as often, we estimate about once a week or so. The nozzles are made for use with no water-pressure, just gravity and they pass through a surprising amount of water. They just wander up and start drinking; no fuss, no muss, and clean water for all!
I'll let the pictures and videos speak for themselves:
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