I just visited a local company who has 6 large wire EDM units cutting some pretty exotic materials. Very high tolerance and finish. The owner uses rain water for his dielectric liquid. Much cleaner and doesn't have the chemicals additives that would mess up the machinery. A typical rain storm of 1" or so gives him a few thousand gallons that is then filtered to get rid of bugs and leaves.
He doesn't want his company name or address listed because of the companies that use his services.??