It will just drain out as fast as you put it in---or close because it will be getting air in the top. Example-----fill your kitchen sink with water-----lay a glass in the water on its side. Now keeping the drinking end under water stand the glass up---upside down-----now lift the glass----it stays full of water until the drinking rim gets out the water----then it dumps. Now get a piece of pipe with both ends open----stand it in the sink water and draw it up towards the facet turn the water on and try to fill it----it want fill just like drilling a hole in this waterer in the top----all the water will go out.