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In this home i bought, the back yard 28 zone system had a gray 3" diameter by 2" high plastic cylinder lying on the ground with a wire bundle going to a valve box in the ground near the wall mounted controller. Some of the zones off my hunter controller are also hooked up to a wire bundle and not the normal red wires and they go to this same valve box. I have not dug into the valve box yet so it all appears to be related to this cylinder and a valve in the box. Everything seems to work ok but I just am not sure what the hell this thing is. Never seen anything like it before. There is no master valve or pump. It almost seems like a float valve or something that was mounted at one time and it is not a rain sensor for controller. When i turn the cylinder upside down I can hear something move inside. Before i dig into this can anyone help. Thanks,Lardog