Either use your distilled water immediately or boil it, this will eliminate co2 ! Remember ph balancing is not about being totally alkaline its about balance we need certain amount of acid to create electrolytic action ! Approximately 80% alkaline to 20%acid!
This is why vitimin d is added to calcium! Dont let the small amount of co2 that collects in your pure and healing distilled water scare you! Scare tactics is the name of the troll game!
(Edit)also give reverse vortexing a try ! Stir the water in one direction getting good vortex then before it stops reverse the spin! This will eliminate the CO2 gas!
(re edit) Im still experimenting with this myself ,but I beleive what PBuddy says is probably true and will have to obtain a pool type pH testing kit myself to get a true reading!