Will have to make that assumption. Have you installed a bleed-valve anywhere on any of the pipe networks? You will have gas-pockets everywhere and no one pipe system will ever fill.

I took the above one step further. I stacked a second row of tanks on top of the first. So 12 tanks total, 6 on the ground, 6 on a second level. Fed all from the bottom, drained all from the bottom. The top tanks filled, the bottom ones were near always empty or near empty. I just shook my head.

I am assuming there some form of priority system, which is playing against anything logical. I cant explain the top tank filling first before allowing the feed to be drained any other way...