we use 5 gal buckets for weight, place 3 1/2 to 3/4 inch pvc ( make these as high as you want your pile to be)in the bucket when adding sackrete . Place these next to the side of the bucket , at 12, 4 and 8 o'clock.
When you start adding the 4 in drain pipe , place it over one of the uprights, and between the other two . this limits how
much the 4 in can move , keep building up , alternating each piece of 4 inch on the uprights, but always let it rest
between the other two. When you get to the top of your uprights , wire the tops together so the 4 in doesn't float off'

good luck

MO