On each feeding/watering you should basically fill each container. Since you should be growing in 5 gallon buckets (3 would suffice, but 5 gives much larger yields for the same amount of work) you'll be using roughly 2 gallons of water per container depending on your medium.

You do realize you can RO at home, yes?

Lets move on - Your in NM, I'm assuming well water - How long has it been since the well tip has been serviced? This typically solves most problems. There are also several types of tips for specific applications, such as too much membrane in the water - There are also 'pre filter' tips that can be used. These methods are all cheaper than purchasing bottled water, and CAN be cheaper than buying a water purifier. If you have a double pump system, you can even do it yourself for next to free (the filtered tips are about $75 - 125). I'll be in SO CO this weekend, not sure where your at in NM, but I'm always willing to lend a hand, especially if your having water issues, no reason for that, even in NM, there is always a solution.

You might be interested in this:
0-1000 Gallons - RainHarvest Systems Online Store for Rainwater Collection, Filtering and Sustainable Re-use.

I personally wouldn't drink the rainwater gathered off my roof without running it through a filter, however, these setups also let you harvest rain water after the soil has filtered it some.

Anyway, just suggestions. Feel free to IM or Email me, if your interested in help with your well, I'm more than willing to lend a hand. (Depends highly on your location)

Good luck!