Episode 6  ·  May 26, 2026
The pH Ceiling
Why your pH keeps climbing — and what’s actually causing it
🎧 Apple Podcasts 🎧 Spotify

You added acid last Tuesday. pH was perfect. You came back Thursday and it was 7.8. You added acid again. Same thing happened. You’re not doing anything wrong. The pool is doing something you haven’t been told about yet.

The answer has nothing to do with how much acid you’re adding. It has to do with physics — and a principle first described in 1803.

What’s Driving Your pH
01
Henry’s Law and Carbon Dioxide
William Henry described the relationship between gas and liquid in 1803. It governs what happens to CO2 in your pool water — and why aeration drives pH up every time, regardless of what chemicals you add.
02
Salt Chlorine Generators and Hydroxide Ion Production
Every time your salt cell runs, it produces hydroxide ions at the cathode as a byproduct of chlorine generation. Those ions drive pH up continuously. Salt pools don’t drift high because of chemistry mistakes. They drift high because of electrochemistry.
03
Total Alkalinity as a pH Buffer
Alkalinity resists pH change. That sounds useful until you understand it also resists your corrections. The practical target for salt pools is 60 to 70 ppm — lower than the industry standard — to allow pH to be managed without fighting the buffer at every adjustment.
04
Why Muriatic Acid — Not Sodium Bisulfate
Dry acid introduces sulfates. Sulfates accumulate. The only exit is dilution. Above 300 ppm combined with calcium, sulfate creates crystal formation risk independent of LSI. Muriatic acid addresses pH without loading the water with a compound that accumulates indefinitely.
What You’ll Take Away
  • Why pH rises continuously in salt pools and what’s producing it at the electrode level
  • Henry’s Law explained in plain language and why it’s relevant to every pool with aeration or water features
  • Why the TA target for salt pools is 60 to 70 ppm — not the industry standard 80 to 120
  • Why muriatic acid is the correct pH reduction tool and what sodium bisulfate does to water chemistry over time
  • Why borates at 50 ppm are an effective complement to pH management in salt pools
  • The connection between pH management, HOCl availability, and the LSI — all three working at once
Referenced in This Episode
  • Episode 2: The 7.5% Rule — Free chlorine minimum relative to CYA
  • Episode 3: LSI Explained — The six variables governing water balance
  • Episode 4: Salt Chlorine Generators — The full electrochemistry of salt pool operation
  • Ask John: poolsscientific.com/ask-john
Next Tuesday — Episode 7
I Saw It on TikTok
Mineral systems. Copper ionizers. Chlorine-free pools. Products that promise to make chemistry simple. What does the science actually say about the alternatives to chlorine — and who benefits when the answer is complicated?
New episodes every Tuesday.
Find us on Apple Podcasts and Spotify. Show notes and resources at poolsscientific.com.