if anyone has 20 Liter buckets and 30 Liter buckets like the Allpack ones then here are the markings to set up the liter marks.
using a permanent marker draw a vertical line on the bucket,
from the bottom of the bucket mark as follow's,
20 liter bucket
81 mm = 5 liter
163mm = 10 liter
238mm = 15 liter
310mm = 20 liter
30 liter bucket
69mm = 5 liter
129mm = 10 liter
187mm = 15 liter
243mm = 20 liter
299mm = 25 liter
ooh be care doing that Mr D, diameters change from time to time :(