I can give real world figures, as I have a sewer meter installed. I have a 4/2. Autos are Nu*Star friction machines with hp pumps. I do have reclaim for the autos only; probably for about 40% of the wash cycle. The most my sewer has ever been reduced by is 17%. The least is 8%. The average is 12%. So my average sewer cost savings per month at this location is $114. (Sewer is $4.75/1000) I have had sewer meter for 10 years, so it has paid for itself.
When I spent the $4k to put the sewer meter in, imagine my surprise at these low numbers. I have never really calculated the water usage by each auto or ss, cause there is really no point in it. We gotta have water to run; so it is what it is. We just always do our best to conserve where possible.
I know that that rain water does get into the drains, as months with a lot of rain my sewer is higher. I would design the building a little differently if I had it to do over. So in theory, the ICA study is probably pretty close on the raw numbers for evap/ carry off.
