Water Chemistry
The water's capacity to resist pH changes, functioning as a buffer. Illinois IDPH range is 60 to 180 ppm; operators target 80 to 120 ppm as a practical working band.
Alkalinity is the backbone of stable pool water. Low alkalinity lets pH swing wildly with every dose of acid or shock; high alkalinity makes pH difficult to move when you need to adjust it. Either drift burns through chemicals and frustrates operators. Corrections are slow. Adding sodium bicarbonate to raise alkalinity takes 24 to 48 hours to fully register. Alkalinity also affects the Langelier Saturation Index; a pool balanced on pH + chlorine alone but unbalanced on alkalinity is still quietly corroding or scaling.
Alkalinity isn't pH. They're related but distinct readings.
You can't raise alkalinity quickly without side effects. Patience is the correct answer.
Chicago-area municipal fill water tends to be alkaline-heavy, so many pools trend upward over time.
Read more on the blog
Related terms · Water Chemistry
Cyanuric Acid (CYA / Stabilizer)
A pool additive that protects chlorine from UV degradation in outdoor pools. Useful in moderation, counterproductive above 70ppm.
Chlorine Lock
A state in which chlorine test readings appear normal but the chlorine is ineffective at actually sanitizing the pool. Usually caused by excessive cyanuric acid.
Combined Chlorine (Chloramines)
Chlorine that has already reacted with organic contaminants and lost most of its sanitizing value. The primary cause of the strong `chlorine smell` in pools.
Langelier Saturation Index (LSI)
A composite calculation (pH + temperature + calcium hardness + alkalinity + CYA adjustment) that measures whether pool water is corrosive, balanced, or scale-forming.
Aqua-Guard runs certified commercial pool operations for Chicagoland HOAs, condos, and clubs. We handle the credentials so your board doesn't have to.
Request a Written Proposal