RO-DI Ph question

[sdfish]

i have a rodi for my new tank i am setting up. i was testing the water coming out of it befor i started filling my tank and it is 6.0.. is this normal or should it be 7? i have calibrated my probe and tried kits to second check it..

 

[bpiermat]

PH for RODI water does not matter...because it has a very low alkalinity.

In simple terms, since the water is so pure any amount of acid (such as a single drop of saliva from your mouth) would have a huge effect on the PH of the water since it has no other elements in it to balance the ions. Thus this water would have a very high PH but a very low alkalinity.

So for example, if a gallon of pure water has a pH of 1.0 (extremely acidic) and it is added to a gallon of water that has lots of free ions, (higher alkalinity) and a pH of 7 (tap water). The result would be 2 gallons with a PH of 7.0. Alkalinity is the measurement that is critical

 

[sjames]

it should be about 7 as soon as it exits the di chamber, but it will get lower as it uptakes co2.

 

[sdfish]

ok that helped alot thank you bpiermat

 

[bpiermat]

Yeah that's right...CO2 in the atmosphere will lower the PH...even the smallest imbalance will change the PH.

 

[AZDesertRat]

There are not enough ions in RO/DI to accurately measure pH, don't fret it as it makes no difference.