Just curious, does someone have a simple (not-too-scientific ) explanation for how the bucket/bottle + saucer waterers operate? Is it some kind of a siphon effect? I have made two small ones that seem similar--each has one small hole below the saucer lip level and I plug the hole while filling. The bucket with 6" lid won't work unless the lid is sealed. The water bottle with 1-1/2" cap won't work unless the cap is loose. Why the difference?