I dilute straight 85% Phosphoric acid acid with 10 parts RO water, but that is really n more because i dispense with a pump and larger volume administratiions are more precise. PH down retail preparations are alrady diluted to a Phosphoric percentage of 35% and Nitric acid of 11.5%. Large doses of the Phosphoric acid could cause some Phosphate precipitation but that would really not be any nmore precipitation than the amount of phosphorous in the acid. It would also take some calcium out of solution with it. The amounts precipitated as far as nutrients are concerned would be negligible. But the precipitates can lead to clogged misters. Diluting with RO water or even juss strirring the nutrient water while adding the acid would eliminate the problem as the precipitation only happens in the immediatte areas where the acid is added if thw water is still water as that specific small area becomes over saturated with Phosphorus. If you have a small circulating pump or use air stones in the reservoir there will be no precipitation either.
Yes adding pH down to concentrated nutrients can cause phophorous precipitation if you are adding it to the Part of a two or three part formula that contains the phosphorus. i.e. With a GH formula or AN two part formula you could add it to the micro, but not to the Bloom or Grow until after they are diluted.
