Muriatic Acid Pool Calculator
Calculate the exact amount of acid needed to balance your pool’s pH
31.45% (Full Strength / 20° Baume)
15.72% (Half Strength / 10° Baume)
10% (Weak / Low Fume)
Standard alkalinity is 80-120 ppm. Higher alkalinity requires more acid to lower pH.
Required Muriatic Acid:
⚠️ SAFETY: Always add acid to water, never water to acid. Wear gloves and eye protection.
How to Balance Your Pool pH with Muriatic Acid
Maintaining the correct pH level (typically between 7.2 and 7.6) is crucial for swimmer comfort and equipment longevity. When pH rises above 7.8, chlorine becomes less effective, and scale can begin to form on pool surfaces. Muriatic acid (hydrochloric acid) is the most common and effective chemical used to lower pH and Total Alkalinity (TA).
Why pH Matters
If your pool’s pH is too high, you may notice cloudy water, skin irritation, and “stinging” eyes. Furthermore, high pH causes calcium to come out of suspension, leading to white flaky deposits known as scale. This calculator determines the precise volume of acid required based on your specific pool volume and water chemistry variables.
Example Calculation
If you have a 20,000-gallon pool with a current pH of 8.0 and you want to lower it to 7.5, and your Total Alkalinity is 100 ppm, you would typically need approximately 26-30 fluid ounces of 31.45% muriatic acid. If your alkalinity were higher (e.g., 150 ppm), you would need significantly more acid to overcome the water’s buffering capacity.
Important Safety Steps
- The “AAA” Rule: Always Add Acid. Slowly pour the acid into the deep end of the pool while the pump is running. Never pour water into a container of acid.
- Wait and Retest: After adding acid, wait at least 4 to 6 hours with the circulation system running before retesting the pH levels.
- Storage: Store muriatic acid in a cool, dry place, away from other pool chemicals (especially chlorine) as mixing them creates toxic gas.
function calculateAcid() {
var volume = parseFloat(document.getElementById(‘poolVolume’).value);
var currentPH = parseFloat(document.getElementById(‘currentPH’).value);
var targetPH = parseFloat(document.getElementById(‘targetPH’).value);
var alkalinity = parseFloat(document.getElementById(‘totalAlkalinity’).value);
var strength = parseFloat(document.getElementById(‘acidStrength’).value);
if (isNaN(volume) || isNaN(currentPH) || isNaN(targetPH) || isNaN(alkalinity)) {
alert(“Please enter valid numbers for all fields.”);
return;
}
if (currentPH <= targetPH) {
alert("Current pH is already lower than or equal to the target pH. No acid needed.");
document.getElementById('acidResult').style.display = 'none';
return;
}
// Base formula: To lower pH by 0.1 in 10,000 gallons at 100ppm TA
// Requires approx 6 fluid ounces of 31.45% Muriatic Acid.
// Alkalinity factor: Higher alkalinity requires more acid.
// Adjustment factor: (Alkalinity / 100) – this is a simplification but accurate for pool maintenance ranges.
var phDrop = currentPH – targetPH;
var baseDosePer10k = 6.0; // fl oz for 0.1 drop at 100 TA
var alkFactor = alkalinity / 100;
if (alkFactor < 0.6) alkFactor = 0.6; // Floor for very low TA
var totalOz = (volume / 10000) * (phDrop * 10) * baseDosePer10k * alkFactor;
// Adjust for acid concentration (31.45% is baseline)
var strengthFactor = 31.45 / strength;
var finalOz = totalOz * strengthFactor;
// Display results
document.getElementById('ozResult').innerHTML = finalOz.toFixed(1);
document.getElementById('cupResult').innerHTML = (finalOz / 8).toFixed(2);
document.getElementById('quartResult').innerHTML = (finalOz / 32).toFixed(2);
document.getElementById('acidResult').style.display = 'block';
}