When I use f90 I don't use nearly as much as it says on the bottle because it foams up to hell, I'd say that to my 12ltr chem solution I put maybe 100ml of f90 and run at between 2 and 4gph, I find this plenty
that would be for moderate to bad carpets, on most jobs though I just use an acid rinse or have the chems off and rinse fresh
A bottle of f90 lasts me ages, that's what I love about it
