I just want to add a couple of photos of progress made on the buffer tank portion of this filter installation. The four 400 l tanks are plumbed in parallel with 1" pvc discharging through a gate valve into the top of the sand filter. I welded the stand from 2" square tubing and flat bar with plastic wood boards for decking.
A view into the filter:
I'm waiting on a rubber grommet to make a nicer connection to the filter basket in the top of the first tank. Then a small amount of plumbing to complete on the discharge side of the filter and it'll be in service!