well i have work out that with my big machine running at 13 litres a minute i could get over an hour from 1000 ltr tank but with my smaller machine i could get 2 hours which is great for doing small patios and drives easy! without need for custyies water supply, also for doing shop fronts like cafe's, pubs etc to save running hoses to kitchen taps or sink taps which is a pain ! what you think?