DIY PH measurement and CO2 Injection System- Project Summary

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FlappyLipps said:
What is causing the ph rise so much if your on vacation?
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It's a new pool and combination infinity/zero edge. LOTs of aeration which causes off gassing and pH to rise... should get better as the plaster cures but I think this pool is going to be an acid consumer long term more so than most pools.

Chrisx
 
I would really consider borates. I have been getting scaling in my SWG even with a negative CSI. The borates are supposed to help with that. I just dumped a bunch of borates in yesterday and I am going away for about two weeks. I will let you know how that works when I get back.
 
Katodude said:
I would really consider borates. I have been getting scaling in my SWG even with a negative CSI. The borates are supposed to help with that. I just dumped a bunch of borates in yesterday and I am going away for about two weeks. I will let you know how that works when I get back.
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I used borates on my previous pool and they worked great. May still have some and I have the chemicals to do the borate test. Need to read up on @JoyfulNoise posts about that test. Never knew they'd reduce scaling. I also never had scaling before... always thought it was because I kept CSI slightly below 0. Thanks and please let us know how you do with borate addition.
 
BTW I made a few changes to the system and it's improved a LOT. I moved the injection point downstream of the pH probe. Even with .1 second pulse of my solenoid valve I'm still getting a pulse of tiny, tiny bubbles after all. Looks like I'm going to need that diffuser @JamesW recommended or at least my home-made version. For now I'm wasting some C02 but definitely controlling the pH still. Day 1 low reading was when I had been fiddling around with the pH probe.

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Borates reduce scaling inside the SWG cell because borates act as a high pH buffer (pKa ~ 9.2) and so the buffering strength is greatest at higher pH. Therefore the water inside the cell cannot get to very high pH which reduces the amount of carbonate ions around and thus impedes the formation of calcium carbonate. It’s hard to estimate but without any buffering the pH near the plates in the cell while generation can go all the way up to 12-13 while borates will clamp the pH to around 10 or so. Given the logarithmic nature of the pH scale, that a huge change in available carbonate.
 
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