Reagent Water Type IV for copper sulphate Test per AMS 2700

A. How much water do you need. Lab supply houses sell it by the jug. If you need more, there are excellent DI rigs that will give you whatever quality of water that you need. You just change out the resin/filters when the quality drops on the meter.
If you are using chlorinated water, run a prefilter with activated carbon ahead of it for longer life.
Running a small RO unit ahead of it will make it last even longer. Think of the under the sink size.

If you need lots and lots of water, then go with multiple mixed resin commercial tanks in series.

A. P.J.,
Thanks for pointing this out. I've read AMS 2700 before of course but it seems I always glossed over the specifics of the copper sulphate formula. Even the original MIL spec 753C (used by QQP35 and as the basis for both 2700 and A967) uses distilled water for this. I cannot fathom why the AMS committee went with D1193 reagent water when 2700 was first crafted. I am on that committee now and have a list of things to bring up the next time 2700 is up for review, I shall add this to that list.

I don't have a copy of D1193, though the ASTM page for one of the older versions (www.astm.org/DATABASE.CART/HISTORICAL/D1193-99E1.htm) happens to list out what limits are associated with the different types. IV is the option with the highest impurity amounts allowed. It would not surprise me if the vast majority of distilled water you can get easily surpasses the requirements for Type IV. However, wording the copper sulphate recipe to require type IV rather than mere "distilled water" in general implies an onus on the user to test the water for these limits or purchase from a source that certifies the limits, and that I think is quite unnecessary.

A. PJ,
It does seem like the SAE committee went out of their way to make the copper sulphate requirements obtuse and difficult.

I don't have a copy of AS2390 handy, but 2700 says "Test specimens of any convenient size, made from materials in accordance with AS2390 representing transformation hardening steels". Since your 300 series parts are not a transformation hardening grade, I do not think this is actually saying you need to use the same alloy as your parts. Something under the martensitic category should be fine here.

Since 2700 does not use the phrase "the same generic class of alloy" at all, I'm not sure how AS2390 is expected to apply here.

A. The easiest way to get the water in small quantities is to buy a disposable Mixed Bed Ion Exchange cartridge from a lab supply company. These have a color change so you can tell when they are exhausted and need to be replaced. The water will meet or be even better than Type IV specifications in quality.