Target ranges
| Reading | Typical target |
|---|---|
| Free chlorine | About 7.5% of CYA (e.g. 3 ppm at CYA 40), never below 1 |
| pH | 7.4 – 7.6 |
| Total alkalinity | 60 – 120 ppm (lower end for salt and liquid chlorine pools) |
| Calcium hardness | 250 – 450 ppm plaster, 200 – 400 vinyl/fiberglass |
| Cyanuric acid | 30 – 50 ppm, 60 – 80 ppm for salt pools |
| Salt | Per the cell manufacturer, usually 2,700 – 3,400 ppm |
How the doses are calculated
Chlorine, alkalinity, calcium, stabilizer and salt doses come from straight chemistry: how much of the active ingredient raises the level by one ppm in the pool's volume, adjusted for the product's strength. For example, 10.2 fl oz of 12.5% liquid chlorine raises 10,000 gallons by 1 ppm.
pH is different. How far a dose of acid or soda ash moves pH depends on the total alkalinity, which acts as a buffer. Flat "oz per 0.1 pH" rules ignore that. This calculator models the carbonate buffer and corrects for cyanuric acid, so the dose fits your water. It doesn't model borates. If the pool uses a borate product, expect to need more acid.
Always retest
Test kits, product strength and pool volume all have some error. Add about three-quarters of a large dose, circulate, retest, then finish. Check the LSI once pH, alkalinity and calcium are in range.