When using RO water to water between fertilizing, does anyone adjust the ph of the RO water. If so what do they use and how much per gallon?

It doesn't matter what the RO water pH is because the buffer capacity is almost zero.

Buffering aside, pH effects nutrient availability. Something around 6.5 will have a full gauntlet of nutrient available.

Kyle

The pH of good quality RO water will measure towards the acid side on a pH meter because of the limitations of the technology. A pH meter converts the ionic flow across its membrane into an electrical signal. However, because of the lack of ions in the RO solution, the signal is so weak the value is esentially false. Pure water at gas equilbrium has a pH of 7.

Also,since there is no buffering capacity of RO water, you can sneeze on it , and the added CO2 will acidify it. Subsequently when its going through a pot, its not influencing the pH of the potting media, but the the pH of the potting media is influencing it. So I wouldn't worry about the pH of RO water for misting and flushing purposes.

If you use acidic substances in your potting mix ( fir bark an sphagnum) and try to run the pH up with buffered water, you will salt up the mix faster than if you start out with a neutral or basic mix (CHC and oyster shell). I guess it all depends on the pH goals of the potting mix and the plant you are trying to grow in it.

Also,since there is no buffering capacity of RO water, you can sneeze on it , and the added CO2 will acidify it.

Now that's how I'm doing it from now on. :wink:

I use straight RO sometimes and I also use a 3 to 1 mix of RO to tap. It depends on which fish tanks I have made water changes in.....some tanks are very acidic while others can vary between 7 to 8. I usually flush all of my orchids once a month in straight RO water.