I found an interesting article on water and RO DI processing:
http://www.reefkeeping.com/issues/2005-05/rhf/index.php
With the following quote about the PH of water after RO/DI filteration:
1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO2. At saturation with the level of CO2 in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO2, and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.
Since we smoke, the CO2 is likely to be higher in our house but the mixing and areated holding buckets are is in the garage (48 hour min time usually 4-5 days but I mix my buffer immediately to the fresh water and use the prebuffered water to make my salt so I have no recent results but have tried not using a buffer anytime I experiemented with new salt with at least a 48 hour delay). We do have very high acid water (great for azailias, magnolias, gardinias and tomatos) which might partially account for the low PH. I will try to remember to set up a little experiment with tap and unbufferred RO water this weekend.
http://www.reefkeeping.com/issues/2005-05/rhf/index.php
With the following quote about the PH of water after RO/DI filteration:
1. The pH of totally pure water is around 7 (with the exact value depending on temperature). As carbon dioxide from the atmosphere enters the water, the pH drops into the 6’s and even into the 5’s, depending on the amount of CO2. At saturation with the level of CO2 in normal (outside) air, the pH would be about 5.66. Indoor air often has even more CO2, and the pH can drop a bit lower, into the 5’s. Consequently, the pH of highly purified water coming from an RO/DI unit is expected to be in the pH 5-7 range.
Since we smoke, the CO2 is likely to be higher in our house but the mixing and areated holding buckets are is in the garage (48 hour min time usually 4-5 days but I mix my buffer immediately to the fresh water and use the prebuffered water to make my salt so I have no recent results but have tried not using a buffer anytime I experiemented with new salt with at least a 48 hour delay). We do have very high acid water (great for azailias, magnolias, gardinias and tomatos) which might partially account for the low PH. I will try to remember to set up a little experiment with tap and unbufferred RO water this weekend.