Acid Dose Estimator (Water pH Adjustment)
How this acid dosage calculator works
This tool estimates how much liquid acid to add when lowering water pH. It uses your water volume, current pH, target pH, alkalinity, and acid strength. The estimate combines two demands:
- Buffer demand: alkalinity resists pH change, so higher alkalinity requires more acid.
- Free proton demand: the direct hydrogen-ion shift between current and target pH.
Because real systems vary by temperature, dissolved gases, and chemistry, use this as a starting estimate and then retest after each adjustment.
Input guide
1) Water volume
Enter total system volume in liters. If you only know gallons, multiply US gallons by 3.785 to convert to liters.
2) Current and target pH
The target pH must be lower than the current pH for acid dosing. For most pools and many irrigation systems, a pH near 7.2–7.6 is common, but always follow your local standards.
3) Total alkalinity
Alkalinity is the major factor in acid demand. Two systems with identical pH can need very different acid amounts if alkalinity is different.
4) Acid strength (normality)
Stronger acid means less liquid volume required. If your product has a known concentration, use the custom normality option for best results.
Safe dosing steps
- Wear gloves and eye protection.
- Ensure circulation pumps are running.
- Add acid slowly to moving water—never splash into still corners.
- Always add acid to water, never water to acid.
- Split larger doses into 2–4 additions and retest after mixing.
Example
Suppose you have 10,000 L of water, pH 7.8, target pH 7.4, alkalinity 100 mg/L as CaCO₃, and muriatic acid (~10 N). The calculator returns an estimated dose in mL and fluid ounces, plus a split-dose suggestion.
Frequently asked questions
Why is this only an estimate?
Real water chemistry includes additional buffering (cyanurates, borates, phosphates, dissolved CO₂). Those effects can increase or decrease actual demand.
Can I use this for raising pH?
No. This tool is for acid additions only. To raise pH, use an appropriate base and a separate alkalinity/pH model.
How often should I re-test?
For routine maintenance, test after each adjustment cycle and again after full circulation. In active systems, daily checks are common.