After many attempts to make over the counter and on line watering systems work I decided to go with my own version, similar to the 8 ounce systems that work on gravity and vacuum, using a 6"x 48" tall PVC pipe with caps glued on each end and a couple fittings drilled, tapped and threaded on the sides and top. I simply plug the bottom hole and fill the tube. With a second rubber plug I place It firmly in the top hole, removing the bottom plug a vacuum is created letting only enough water out to cover the hole. It holds nearly 6 gallons of water, plenty to last my flock a couple days. And never needs cleaning as poultry reach through the wire to dip a beak, no poop water works for me.