You un-thread the plastic bolt on the bottom center, disassemble the valve (ball cock) and have to keep it spotless. I'm in Fl, our well water turn to algae in two days. The slime builds up in the bottom chamber and breaks the vacuum seal-thus leaking out the contents of the whole set up. Then your birds are dehydrated from the heat and having no water to wash down the feed they ate.I was under the understanding that this model used a float valve, or simular and not vacuum?
One of our floats filled up with water from a poor seam in the plastic. It had to be glued tight. It was only a month old at that time. I switched to metal water hangers and never looked back.