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Pool Chlorine Dosage Calculator

Liquid Chlorine (10% Sodium Hypochlorite) Liquid Chlorine (12.5% Sodium Hypochlorite) Cal-Hypo (65% Granular) Dichlor (56% Granular) Trichlor (90% Tablets/Granular)

Calculation Result

function calculateChlorineDosage() { var volume = parseFloat(document.getElementById('poolVolume').value); var current = parseFloat(document.getElementById('currentPpm').value); var target = parseFloat(document.getElementById('targetPpm').value); var type = document.getElementById('chlorineType').value; var resultDiv = document.getElementById('chlorineResult'); var output = document.getElementById('dosageOutput'); var ppmText = document.getElementById('ppmChange'); if (isNaN(volume) || isNaN(current) || isNaN(target) || volume <= 0) { alert("Please enter valid positive numbers for volume and chlorine levels."); return; } var increaseNeeded = target – current; if (increaseNeeded <= 0) { resultDiv.style.display = "block"; output.innerHTML = "No Chlorine Needed"; ppmText.innerHTML = "Your current chlorine level is already at or above your target."; return; } var dosage = 0; var unit = "ounces"; // Formulas based on 10,000 gallons to raise 1 ppm // Liquid 10%: ~12.8 oz // Liquid 12.5%: ~10.2 oz // Cal-Hypo 65%: ~2.0 oz // Dichlor 56%: ~2.4 oz // Trichlor 90%: ~1.5 oz if (type === "liquid10") { dosage = (volume / 10000) * increaseNeeded * 12.8; unit = "fl. oz (Liquid)"; } else if (type === "liquid12") { dosage = (volume / 10000) * increaseNeeded * 10.2; unit = "fl. oz (Liquid)"; } else if (type === "calHypo65") { dosage = (volume / 10000) * increaseNeeded * 2.0; unit = "oz (Weight)"; } else if (type === "dichlor56") { dosage = (volume / 10000) * increaseNeeded * 2.4; unit = "oz (Weight)"; } else if (type === "trichlor90") { dosage = (volume / 10000) * increaseNeeded * 1.5; unit = "oz (Weight)"; } resultDiv.style.display = "block"; output.innerHTML = "Add " + dosage.toFixed(2) + " " + unit; ppmText.innerHTML = "This will increase your chlorine by " + increaseNeeded.toFixed(1) + " ppm in a " + volume.toLocaleString() + " gallon pool."; }

How to Use the Pool Chlorine Calculator

Maintaining the correct chlorine level is the most critical part of pool maintenance. Chlorine acts as a primary sanitizer, killing bacteria, algae, and organic contaminants. This calculator helps you determine exactly how much product to add to reach your desired Free Chlorine (FC) level.

Understanding Chlorine Types

Not all chlorine is created equal. The amount you need depends on the concentration of the active ingredient:

  • Liquid Chlorine (Sodium Hypochlorite): Usually found in 10% or 12.5% concentrations. It is easy to add but heavy to carry. It does not add Cyanuric Acid (stabilizer) or Calcium to the water.
  • Cal-Hypo (Calcium Hypochlorite): A granular chlorine that typically contains 65% chlorine. Note that it increases Calcium Hardness levels over time.
  • Dichlor: A stabilized granular chlorine (56% concentration). Use this carefully as it rapidly increases Cyanuric Acid levels.
  • Trichlor: Highly concentrated (90%) and stabilized. Usually found in 3-inch tablets. It is very acidic and also raises Cyanuric Acid.

Step-by-Step Dosage Guide

To get the best results from your pool chemicals, follow these steps:

  1. Test Your Water: Use a high-quality liquid reagent kit or test strips to find your current Free Chlorine level.
  2. Determine Pool Volume: If you don't know your volume, multiply Length x Width x Average Depth x 7.5 (for rectangular pools).
  3. Set Your Target: Most residential pools should maintain a Free Chlorine level between 2.0 and 4.0 ppm.
  4. Calculate and Distribute: Use the calculator above to find your dosage. Add liquid chlorine by pouring it slowly in front of a return jet. For granular chlorine, it is often best to pre-dissolve it in a bucket of water before adding it to the pool to prevent liner staining.

Practical Example

Suppose you have a 20,000-gallon pool. Your test kit shows 1.0 ppm of chlorine, but you want to reach 3.0 ppm for the weekend. You are using 10% Liquid Chlorine.

The calculator determines you need an increase of 2.0 ppm. Using the formula: (20,000 / 10,000) * 2.0 * 12.8 = 51.2 oz. You would need to add approximately 51 ounces (or about 1.6 quarts) of liquid chlorine to your pool.

Safety Warning:

Always wear eye protection and gloves when handling pool chemicals. Never mix different types of chlorine together in the same bucket or feeder, as this can cause a violent chemical reaction or explosion.

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