We are building some movable hoop coops to pasture our flocks. In the main coop we have always used normal watering systems that you fill and it flows out the bottom to fill the rim. In the hoop coops I am considering using the horizontal nipples attached to PVC pipe that well be gravity fed from a five gallon bucket. How many nipples do I need (nipples per population) and what should the spacing be between nipples? Each coop will house 10-12 chickens.