Free tool
LSI calculator
The Langelier Saturation Index tells you if your water is corrosive, balanced or scaling. Enter your readings — the math is done for you.
+0.03
balanced
For illustration. Splashr calculates LSI and suggested doses for every visit.
How to read your result
Below −0.30
Corrosive
Water is hungry. It etches plaster, eats heaters and corrodes metal fittings. Raise pH, alkalinity or calcium.
−0.30 to +0.30
Balanced
The sweet spot. Water is stable, sanitizer works efficiently and surfaces stay protected.
Above +0.30
Scaling
Water drops calcium onto tile, salt cells and heaters. Lower pH or alkalinity before scale sets in.
Field tips
- CYA counts: high stabilizer lowers your effective alkalinity — this calculator adjusts for it.
- Temperature matters more than most techs think. Hot spa water scales at the same readings that were fine in the pool.
- Test weekly, and always after heavy rain, a big top-off or a algae treatment.
This calculator lives on every stop in Splashr.
Readings, doses and LSI history saved per pool — no paper, no guessing.
Start free — 60 days on us