I did a lot of calculations before deciding on the what and how-many of our cisterns. I also sought expert advice. I met Nikola Davidson, the one-woman show that is Earth Systems Northwest, through a mutual friend. In addition to numerous emails, Nikola came out for site visits twice to advise. She ultimately ordered our tanks, arranged their delivery, and provided the plumbing parts.
The tanks are big (cylinders 4′ wide by 6′ tall). They aren’t heavy, but they are awkward to move. Our yard is fenced and none of the gates are 4′ wide. So the tanks had to go up and over; easier in the front (4′ tall) than the back (6′ tall):
Water is heavy. At 1 g/mL, each of our 500-gallon cisterns will weigh >4000 pounds when full. Four tons. Wow.
Point being, we needed to create solid bases for our cisterns. Options include poured concrete pads, cinder blocks, crushed gravel or sand. We decided on crushed gravel (5/8″ minus) in a wooden frame.
It took a surprising amount of gravel to fill our three 4′ x 4′ frames – about 20 cubic feet (27 cu.ft is 1 ‘yard’). I had calculated less, but did not factor the compaction of tamping down the gravel.
The first two bases were easy; screw together frames, level, fill with gravel, tamp down, place cistern. Plumb.
The third cistern required more time as it was ‘in the way’ of our current path through the chicken yard. We had toiled considerably to install the brick pathway, but it had issues anyway, being a bit low and a bit narrow.
So the one fine day this weekend, up it came. We built the cistern base into the new, expanded pathway, the chickens had a worm day, working the exposed soil, and everyone was tired but content by sunset.
It has been a rainy March. The head tank remains empty, but Cistern 1, installed mid-March now contains 150 gallons. And Cistern 2 is filling as well. I will post again when we pump to the head tank!