From experience in wine, chilling is always done with a brine solution, not water. Any micro brewer or bigger, in my view, would be crazy not to be using a material that is -5C to chill - especially on big volumes. Most the water usage is on cleaning, which I feel is acceptable as a spoilt batch of 10,000L is a bigger loss than me losing 35L!
Anyway, we are currently thinking of having a gently sloped copper piping (maybe SS if our hook up comes through...here's hoping) in an old esky filled with ice (or freezer blocks that we can continually refreeze). We figure if this doesn't work we can go and refit it as an immersion chiller. Pics in a few weeks! Holla!