This article is from the Water for coffee FAQ, by Jim Schulman with numerous contributions by others.
With conventional water inlet design, a commercial operation
needs to run boiler safe water. This may have a slightly deletorious
effect on espresso taste, and still necessitates boiler blowdowns.
However, if the demand were out there, it shouldn't be all
that difficult to design a better system. It would run two levels of
water: RO water with a tad of minerals into the steam boiler, and a
harder, tastier water into the heat exchangers. With proper plumbing,
it should be simple to do a nightly citric acid flush of the heat
exchangers, and a monthly boiler flush to keep them scale free.