Yeah, been running my tanks off a well for 19 years. Water quality varies wildly, so understanding your starting point is useful. For example, my raw water shows a TDS of about 350, but my neighbor (also a reefer) measures over 800. Pauly's right that well water eats though DI resin fast. I assume its because of dissolved CO2, which can be blown off, though I have not bothered to do so. I get probably 200 gallons off a single BRS DI charge (at incoming TDS of about 7). Booster pump can help, though the newer well pumps can get up above 60 psi and not need one.