High ph and High Alkalinity
I just set up my 18 AG for the summer and I have a couple of questions.
Here are the specs for my fill water from my well (I have a water softener)
ph
7.2
alk
260
hardness
0
After adding the correct amount of bleach and cyanuric acid, and running the pump for three days and aerating.
cl
3 ppm
ph
8.2
alk
260
cyn
40 ppm
hardness
0
I know I need to add some ph- to bring my ph down and continue to aerate.
My questions is why would after adding cyanuric acid would my ph go up? From what I remember from college chemistry acid should reduce ph.
Re: High ph and High Alkalinity
CHEMISTY NERD ALERT!
Once the CYA dissolves in the water it becomes part of the buffer system (cyanuric acid/cyanurates). It will cause the TA reading to go up. You have been airating which also causes the pH to rise and decreases the TA...however you are not correcting for the CYA in the TA reading. At a pH of 8.2 your CYA correction factor is about 3.6 which you multiply by your CYA level of 40. (the correction factor changes with pH) This gives about 14 which you then subtract from you ALK to get a corrected ALK of 246. You have actually lowered your ALK since ALK is really a measure of the carbonate hardness in the water (carbonic acid/carbonates/bicarbonates) and any secondary buffers such as cyanuric acid/cyanurates and boric acid/borates are not a part of this system even though they will test as such on the ALK test.
This explains why your TA has not seemed to lower even though you dropped the pH and airated. The rise in pH was not from the CYA. It was caused by gassing off CO2 by airation thereby reducing the amount of carbonic acid in the buffer system and since the carbonates and bicarbonates are now in a higher ratio to the carbonic acid your pH went up.
The jury is still out on whether this correction for CYA is useful or not. IMHO it is not.
I usually disreguard the correction factor, adjust CYA first, and then adjust TA!
My advice would be to lower the pH again to about 7.0 to 7.2, airate, and recheck the Ta until it is in the proper range.
