I have a 25K inground fiberglass-concrete pool (painted with expoxy paint).
I bought an aquarite-pro with 40K cell a few months ago. It works perfectly (purchased from inyopool they gave me a good deal beating the competition..). Two weeks ago I bought a sense-dispense kit (from ezpoolz) and hooked it up.
Warning: the plastic of the plastic case is quite stiff so the normal teflon tape tends to tear with associate leaks. I am currently using the thicker yellow teflon (the one for gas lines). No leaks.
Anyway, the PH probe is perfect. I calibrated with a buffer solution that we use for reference in my place and it is straight to the digit. The PH probe controls a stenner acid pump. I will switch to CO2. I`m aware that it will cost more (0.5-1lb of CO2 per day) but safety is important (especially because I`ve already got burned in a fire and I do not want to experience endless pain anymore).
Well, the ORP probe has some issues. It reports 770mV regardless of FC. With FC 0-1-2-3 it always says 770mV.
My CYA is 80 (suggested by the aquaritepro), so I`m wondering if the CYA can fool the ORP so much. Hayward says that I have a defective ORP and they are sending me a new one. Let`s see.
Anyway, the numbers are CYA=80 TA=90 CH=250 ph=7.4 T=67F.
BTW, if you want the saturation index, I rearranged the formula to have the ph which gives zero saturation.
If T is in F, TA,CH are in ppm (and log is natural log), then the correct ph is
For instance with the above numbers I get
Hence ph=7.2 will be the min (corrosion under) and ph=7.6 will be the max (scale above).
Since I do not want to go beyond 7.8 (copper comes off solution) and under 7.1 (epoxy paint chalks too fast), then I`ve a functional which connects CA,TA, and T: ph(CA,TA,T)=optimun=7.4
As CA is fixed (calcium goes away very slowly with leaks or backwash), and T changes during the year (slowly, remember that the specific heat of water if big and near freezing is infinite), then I have a rule connecting T with TA (with the +-0.2 tolerance given by the saturation index range). Finally I plan to make some simple diagrams TA versus T at fix ph and CA so that I see how I need to tune TA to keep the saturation index in the perfect positon.
Well, to make things simple, the water of the pool has never been so clear (borax helps too) and transparent.
Now I need to:
1) wait to fix ORP so I have automatic Cl generation (otherwise I switch to % and that`s it).
2) observe for the next several weeks how TA drifts so I understand how to keep SI in the right range. SI and PH are linearly related so if I do functional derivative of ph versus TA I also get the range of TA to keep the SI in line.. The power of math.
3) find out if TA drift with acid or CO2 are in the same direction. I would prefer if TA goes naturally down as adding baking soda is cheaper than areating... and waiting.
BTW, I plumb, glue, install, program, things by myself. It must be age: I developed a strong allergy to contractors. I am cheaper (think about how many hours you have to work in your job to make 100$/your after taxes to pay 1 hour of some unliterate contractor who has no clue of what he/she is doing) and I am more precise.. and things work ! The last pool contractor I had is still waiting for 1/2 of the bill. I did put a few internet cameras and I proved that he was NOT working the hours that he was charging. I gave him the option: take 1/2 or meet in court. After he threaten me and wish me bad diseases he chose the 1st option... Security cameras.. a good investment against thieves.