I think you'll find the only debate on the water will be whether it should be distilled or dionized. Most well water has small inorganics that can precipitate out. We call it 'hard water' if it has a lot. Public water also has things like chlorine. Not alot but enough. I'm pretty sure you'll have little trouble finding an additive locally or at least easily brought in.
Ask if the the corrosionb inhibitors are inorganic or organic acid technology. If its the latter, then I think its best to make the catch can into a recovery can so no air gets into the radiator.
