RO/PH 7.8 ?

[SSTurner]

Hi all, I am not sure whats up here. My PH is 7.8 in my RO water holding tank (55gal. plastic drum). I changed the 3 lower membranes but not the TFC membrane. Unit is 1yr old and I fill the holding tank about 1 time a week. PH from tap is 7.2 Steve

[Carol_Roberts]

It's is difficult to get an accurate pH readikng from RO water. When you add it to your tank what is the tank pH?
CArol :heart1:

[Steve_Warner]

Hi all,
Steve, What is the purity of your R/O water(do you have any equip to measure it)? Also, how are you measuring the pH(elec. meter, titration drops,)? You WILL NOT get an accurate reading with an electronic meter in very pure R/O water(less than 10uS) due to the constantly changing chemical composition of the water. The ionic equation (H3O+ & OH- = H2O + H2O) is constantly shifting back and forth(but favoring the H2O side) in water bodies with high purity, thus skewing the pH of the sample. An absolutely neutral pH in the exclusion of air(in theory) will have the EXACT same number of Hydronium ions(H30+) as Hydroxide ions(HO-), which makes sense why it would be neutral, as the two different ions are responsible for up(HO-) and down(H3O+) sides of pH. HTH

Steve

[SSTurner]

Steve, I use a Sharp Tester for both PH and TDS from Pet Warehouse.(elec.) I know its not the best but last year it did read 7.1. and still reads my tap right (I think). The purity of my water ? I just check the PH and TDS (TDS says 11ppm). It's 155 ppm from tap. Carol I will give my tanks a w/c and see in a few days because I used tap water in them because my readings from my RO water said it was 7.8 Thank you both.

[RandalB]

I'd say that it was a test anomaly. A 1 year old TFC membrane should be fine given proper maintenance. When I test my RO water it is anywhere from 6.2 to 7.5 on any given test. When I add Tap water it stabilizes at 6.8.


RandalB

BTW, Even if it is 7.8 that's fine for raising and breeding discus