Salt Pool Formula
The Formula
Salt to add (lbs) = (Target ppm − Current ppm) × Volume (gal) × 0.0000834
| Symbol | Description | Unit |
|---|---|---|
Target ppm | Desired salt concentration (typically 3,000–3,200 ppm) | ppm |
Current ppm | Current salt level measured by test strip or system display | ppm |
Volume | Pool volume in gallons | gallons |
0.0000834 | Pounds of salt per ppm per gallon (1 lb salt per 120 ppm per 10,000 gal) | lbs/ppm/gal |
Worked Example
Example
Salt pool: 20,000 gallons. Current salt: 2,400 ppm. Target: 3,200 ppm. System minimum: 2,700 ppm.
- Increase needed = 3,200 − 2,400 = 800 ppm
- Using the rule: 1 lb raises 10,000 gal by 12 ppm
- lbs per 10,000 gal for 800 ppm = 800 ÷ 12 = 66.7 lbs
- For 20,000 gal: 66.7 × 2 = 133 lbs
You need approximately 133 lbs of pool salt — that's about 3.3 bags of 40-lb salt. Purchase 4 bags and add 3.3 bags worth.
How This Formula Works
Salt chlorinator systems require a specific salt concentration to generate chlorine effectively. Below the minimum, chlorine production drops. Above the maximum, the salt cell can be damaged.
- Most systems operate at 2,700–3,400 ppm. Check your system manual for the exact range.
- Pool-grade salt is 99.8%+ pure sodium chloride — do not use rock salt or water softener salt with additives.
- Salt does not evaporate. It only needs to be replenished after significant water loss (drain, splash-out, backwash) or heavy rainfall (dilution).
- 1 lb of salt per 10,000 gallons raises salt level by approximately 12 ppm.
Limitations & Notes
Do not add salt directly to the skimmer or in front of the salt cell. Broadcast evenly around the pool perimeter with the pump running. Allow 24 hours for full dissolution before testing or adjusting again.
Last reviewed: 2026-06-01