Find out in seconds whether your pool water is corrosive, balanced or scaling. Same math as the RouteSplash field app.
The LSI answers one question: will this water take calcium from the pool, or leave calcium on it? A negative number means the water is hungry for calcium. It etches plaster, pits grout, eats heater copper and turns pebble finishes rough. A positive number means the water is carrying more calcium than it can hold, so it drops scale on the tile line, inside salt cells and on heat exchangers.
Four readings drive it, plus temperature: pH, calcium hardness, total alkalinity and water temperature. That is why a pool that tested balanced in March can be scaling by July with no chemical added; the water simply got warmer.
A single reading tells you little. The trend tells you when a customer's plaster is being eaten or a salt cell is scaling up months before it fails. RouteSplash calculates LSI automatically each time a tech logs a reading, charts it per pool, and flags water that has been out of balance for weeks. Pair this with the chemical dosing calculator to see how much to add.
Between -0.3 and +0.3 is balanced. Below -0.3 the water is corrosive and pulls calcium out of plaster, grout and metal; above +0.3 it is scaling and drops calcium onto surfaces, tile and heater exchangers.
LSI = pH + temperature factor + calcium hardness factor + total alkalinity factor - 12.1. The factors come from published lookup tables; this calculator interpolates between table points, the same way the RouteSplash app does.
Yes. Stabilizer contributes about one third of its ppm to the total alkalinity reading without buffering like carbonate does, so pools with high CYA are more corrosive than the plain formula shows. Enter your CYA and the calculator also shows the corrected number.
The fastest lever is pH. Raising calcium hardness or total alkalinity raises the LSI too, and warm water raises it on its own, which is why balanced spring water can scale in a Texas August.
Pool service software built by a working pool company: day sheets, water chemistry with LSI and dosing, chemical billing, AutoPay, profit by route. $49 a month (Starter) up to 50 pools, then $59 + $30/login + $0.25/pool, then $0.75/pool past 150. Try it free for 30 days.
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