I have a Little Giant 3-gallon double-wall fount and can't figure out why it is leaking. It's on the wooden floor of the coop, and I finally took it out because the floor and shavings were soaked. Tried several times to refill it. Filled it, put it in place, put the sleeve over the top, and it filled to a reasonable level. But when I come back a few hours later, it has overflowed. Does anyone know what I'm doing wrong? Thanks.