Ross Simon of Bitters & Twisted Cocktail Parlour in Phoenix, Arizona uses a nano-filtration system at the bar. This system not only filters water for drinking water, it can be adjusted for many different uses at the bar.
According to Wikipedia, "Nanofiltration (NF) is a relatively recent membrane filtration process used most often with low total dissolved solids water such as surface water and fresh groundwater, with the purpose of softening (polyvalent cation removal) and removal of disinfection by-product precursors such as natural organic matter and synthetic organic matter."
Simon writes his reasons for using this system:
1. It uses less water that normal regular systems (better for arid climates with crap water)
2. It prevents lime scale and other build ups [on equipment, which can cause cleaning issues and eventually clogs] compared to carbon filters.
3. It has controllable TDS [total dissolved solids, or mineral content] to make the water flexible for beer, coffee, and ice machines.
4. It produces bottle-quality water for all applications (dilution, ice, pasta, syrups etc.)
5. It allows for better quality gun sodas, which can increase profitability.
6. It produces a smaller carbon footprint comparatively to shipping water bottles over the globe.
7. It allows you to use less chemicals with glasswashers.