I've already written that the solution is strongly acidic, so that fluctuations of ph of the water is negligible. In my terms I pour 1.5 ml of pH Down GHE per 1 liter of water (tap water with 150 ppm). I give to stand for at least 1 day, ph is fixed around 4.5. Then I make the compote to the tank. Two days ago I set the compressor Resun AIR-1000 72l. / H and poured a full tank. Now I watch when it begins to deteriorate.