1500lt/day is some usage!! How many vans?
We used to run 5/6 vans with 400lt tanks off a single 40-40 with booster pump and 2 1000lt IBC's connected together.
Was more than enough - with completely automatic fill/flush the tanks were rarely more than half empty.
5/6 vans doing how much work per day though Ian?
We are all different with the amount of work we cover each day.
I know for a fact my vans use more than 250l a day, it is more towards 400 mark daily and over 500 on the odd day couple of times a month
I dont think 1500 a day is that excessive if working 8 hours normal working day for three vans.
a 4040 could easy cover 3000l a day and then some.
My advice would be bite the bullet and get a 4040 and a good pump after all this is the key ingredient to you making money. then when you need to upgrade again add another 4040.
I stoppped using ibcs now and have upright tanks as they take up less floor space (just cost about 5 times more)
Never could understand why people went for the cheapest ro they could rather than getting one they could grow into, you would not go and buy clothes to small and then try to shrink