i installed a stealth 100 ro system.i have well water.my water without anything comes out around 7.5 to 8 ph and ec of .51 ms.i installed my system last week and the first few gallons were around 6.0 ph and ec of .02 ms.my ec is still .02 but the ph is right around 5.0 to 5.4.i am using drops for the ph since my meter is too undependable.i thought ro systems are not supposed to change the ph.does anyone have any idea why the ph is drifting so much?i installed the ro system due to lock out problems i have been having since starting here in my new home.i am now growing in soil since my ph was swinging too much for my ppk system.any and all help is always appreciated.
-
As of today ICMag has his own Discord server. In this Discord server you can chat, talk with eachother, listen to music, share stories and pictures...and much more. Join now and let's grow together! Join ICMag Discord here! More details in this thread here: here.
ph swings after reverse osmosis treatment
- Thread starter 420ish
- Start date
Google is your friend 
copy & paste
Q : How does reverse osmosis affect pH?
A :
RO product water can have a lower pH than the feed water. It depends on the level of dissolved CO2 in the feed water. A lowering of pH can occurr because the existing CO2 in the water, being a gas, passes through the membrane but the alkaline constituents, primarily HCO3 (bicarbonate), are removed as part of the reject water. In the feed water the HCO3 neutralizes the acid-causing CO2. In the product water, with HCO3, greatly reduced, the CO2 is free to combine with the H2O to form carbonic acid: CO2 + H2O > H2CO.
Another reason to question the pH reading is that for any water sample which is very low in TDS it is very hard to obtain an accurate pH value. The worst case of this accuracy problem occurs with de-ionized water but some low TDS RO water will react the same. The sample is so low in minerals that there is no buffer. The slightest absorption or loss of CO2 shifts the pH substantially. The water’s tendency to pick up additional CO2 from the ambient air, even if the test is done on site, can produce a very low false pH.
In reality, measuring the pH of RO water is difficult and not accurate due to lack of any pH buffering the RO water. If the feed water has a lot of dissovled CO2 then pH can drop a few points. But, in the case of a drinking water RO system, a post re-mineralization filter will help neutralize the final product water's pH level. In the case of RO water for horticultural purposes, once you mix a calcium/magnesium supplement into the RO water and then add your nutrients and additives, the final pH can be adjusted and your feed formula should be pH stable.
- See more at: http://www.hydrologicsystems.com/faqs/faq.php?id=34#sthash.64Ofbtjv.dpuf
copy & paste
Q : How does reverse osmosis affect pH?
A :
RO product water can have a lower pH than the feed water. It depends on the level of dissolved CO2 in the feed water. A lowering of pH can occurr because the existing CO2 in the water, being a gas, passes through the membrane but the alkaline constituents, primarily HCO3 (bicarbonate), are removed as part of the reject water. In the feed water the HCO3 neutralizes the acid-causing CO2. In the product water, with HCO3, greatly reduced, the CO2 is free to combine with the H2O to form carbonic acid: CO2 + H2O > H2CO.
Another reason to question the pH reading is that for any water sample which is very low in TDS it is very hard to obtain an accurate pH value. The worst case of this accuracy problem occurs with de-ionized water but some low TDS RO water will react the same. The sample is so low in minerals that there is no buffer. The slightest absorption or loss of CO2 shifts the pH substantially. The water’s tendency to pick up additional CO2 from the ambient air, even if the test is done on site, can produce a very low false pH.
In reality, measuring the pH of RO water is difficult and not accurate due to lack of any pH buffering the RO water. If the feed water has a lot of dissovled CO2 then pH can drop a few points. But, in the case of a drinking water RO system, a post re-mineralization filter will help neutralize the final product water's pH level. In the case of RO water for horticultural purposes, once you mix a calcium/magnesium supplement into the RO water and then add your nutrients and additives, the final pH can be adjusted and your feed formula should be pH stable.
- See more at: http://www.hydrologicsystems.com/faqs/faq.php?id=34#sthash.64Ofbtjv.dpuf
ptfarmer420
Member
Nice info dansbuds. Thanks 
