Water Hogs

YRNEH
YRNEH Forum Participant Posts: 5
edited March 2013 in Caravans #1

In the April issue of Practical Caravan magazine, on page 10 a contributer says tha twhilst  on site she uses two water hogs, one on the ground and the other raised up on a breeze block. She connects a hose between them and puts the caravan water pump in
the lower hog. As the water is used from the lower hog, it refills from the upper hog. How does this work? I would have thought the water in the upper hog (assuming it is full) would have syphoned out and overflowed from the lower hog. I'm sure somebody has
an explanation. Henry.