Finding ultra-pure water locally...

I have a 180 gallon saltwater aquarium with a 55g sump and had to purchase an RO/DI unit due to well water. They are not expensive. I think mine was less than $150 for a 75 gallon-per-day. I need to add nearly 2 gallons a day due to evaporation and I do a 35 gallon water change monthly. Remember, it takes about 4 gallons to make 1 gallon of filtered water. I have the "waste water" going to my washing machine. Do not store in any ole plastic jug. Glass or a #6 plastic container will not leech. Not a bad idea to own a unit for drinking and getting out all of that garbage that they treat with. You should only drink "RO" and not "RO/DI". Most units have simple valves for using either/both. That will be the day that I pay(get ripped-off) for water!

Jtimothya, maybe it's naive on my part, but I figured that whatever sort of storage container the Reagent water has been stored in to date will be fine for continued storage at home. So that's what I am planning on doing unless I find it's a bad idea...

Guys, I have had a home RO filter for 30 years. It get replaced once a year. At the end of the year the water has about 300 non-water parts per million. After it is replaced this is 3 per million. Our chemistry department has a much higher quality RO device. They certainly were not impressed with my home results but did not mention what theirs yielded.

Hdm, assuming that you meant to add distillation to reagent water, I cannot imagine that adding salt back in as a softener would be used.

Cello, my tests also show that ultra pure water is superior at least as a final rinse to RO water.

Tbg: My comments regarding distillation were only with respect to the fact that distilled water is a far cry from ultrapure as the original poster intimated (ie. ultrapure, lab grade, triple distilled all essentially being the same).

With respect to softening, it can be and is often used as the very first stage (followed by 5 or 6 others) in producing ultrapure water.

Hdm, the reason we have a RO device is that the sodium content of our water is quite high, but it could not be softer or we would never get soap off our bodies. I would just imagine that even a home RO machine would easily get lime or other minerals out of the water as easily as it would get salts out.