Concentration of bleach/hypochlorite in tank (Common: 5.25%, 10%, 12.5%)
Recommended Feed Rates
Gallons Per Day (GPD):–
Gallons Per Hour (GPH):–
Milliliters Per Minute (mL/min):–
Pure Chlorine Required:–
What is Used to Calculate the Chlorinator Feed Rate Setting?
Calculating the correct feed rate for a chlorinator is a critical task in water treatment, swimming pool maintenance, and agricultural irrigation. The feed rate determines how fast your chemical metering pump must operate to inject the correct amount of chlorine solution into the water stream to achieve a specific concentration (dosage).
The Golden Formula:
Feed Rate (GPD) = (Flow (GPM) × Dosage (PPM) × 1440) ÷ (Solution Strength % × 10,000)
Key Variables in the Calculation
To accurately set your metering pump, you must define three primary variables. These are the specific metrics used to calculate the chlorinator feed rate setting:
1. System Flow Rate (GPM)
This is the volume of water passing through the pipe where the chlorine is being injected. It is typically measured in Gallons Per Minute (GPM). If you do not know your flow rate, you cannot calculate an accurate dosage. In variable flow systems, proportional control pumps are often used to adjust the feed rate automatically as GPM changes.
2. Target Dosage (PPM)
The dosage is the concentration of chlorine you want to add to the water, measured in Parts Per Million (PPM) or milligrams per liter (mg/L).
Drinking Water: Often 0.5 to 4.0 PPM.
Shock Chlorination: Can range from 50 to 200 PPM.
Poultry/Livestock: Often 2 to 5 PPM depending on water quality.
Note that Dosage is different from Residual. Dosage is what you add; residual is what remains after the chlorine has reacted with contaminants (chlorine demand).
3. Solution Strength (%)
This refers to the concentration of the chlorine liquid in your solution tank. Using the wrong percentage in your calculation is the most common error.
Household Bleach: Typically 5.25% to 6% sodium hypochlorite.
Industrial Liquid Chlorine: Typically 10% to 12.5% sodium hypochlorite.
Calcium Hypochlorite Tablets: Often 65% (must be dissolved into liquid form first for liquid feed pumps).
Why Specific Gravity Matters
While the standard formula above is sufficient for most field applications, precision calculations technically require the Specific Gravity (S.G.) of the solution. Water has an S.G. of 1.0. Industrial bleach (12.5%) is heavier, with an S.G. of approximately 1.2.
The calculator above provides a volumetric estimation (gallons) which is the standard unit for buying and setting metering pumps (like Stenner or Pulsafeeder pumps). If your pump is rated in GPD (Gallons Per Day), the result matches your dial setting directly.
Example Calculation
If you have a well pump producing 20 GPM, you want to achieve a dosage of 3 PPM, and you are using 6% household bleach:
Multiply Flow × Dosage × 1440 (minutes in a day): 20 × 3 × 1440 = 86,400.
Multiply Strength × 10,000: 6 × 10,000 = 60,000.
Divide the top by the bottom: 86,400 ÷ 60,000 = 1.44 Gallons Per Day (GPD).
You would then set your metering pump to deliver 1.44 GPD.
function calculateFeedRate() {
// Get input values
var flowRate = document.getElementById('waterFlow').value;
var ppm = document.getElementById('targetDosage').value;
var strength = document.getElementById('solutionStrength').value;
var resultsArea = document.getElementById('resultsArea');
// Validation
if (flowRate === "" || ppm === "" || strength === "") {
alert("Please fill in all fields (Flow Rate, Dosage, and Strength).");
return;
}
flowRate = parseFloat(flowRate);
ppm = parseFloat(ppm);
strength = parseFloat(strength);
if (flowRate <= 0 || ppm < 0 || strength <= 0) {
alert("Please enter valid positive numbers.");
return;
}
// CALCULATION LOGIC
// Formula: Gallons/Day = (GPM * PPM * 1440) / (Strength% * 10,000)
// 1440 is minutes in a day.
// 10,000 converts percentage to decimal and aligns units roughly assuming SG close to water.
var numerator = flowRate * ppm * 1440;
var denominator = strength * 10000;
var gpd = numerator / denominator;
// Convert GPD to GPH (Gallons Per Hour)
var gph = gpd / 24;
// Convert GPH to mL/min
// 1 Gallon = 3785.41 mL
// 1 Hour = 60 minutes
var mlMin = (gph * 3785.41) / 60;
// Calculate Pounds of Pure Chlorine per day (for context)
// Lbs = Flow(GPM) * 8.34 * 1440 * (PPM / 1,000,000)
// Simplified: GPM * PPM * 0.012
var lbsPure = flowRate * ppm * 0.012;
// Display Results
document.getElementById('resGPD').innerHTML = gpd.toFixed(3) + " GPD";
document.getElementById('resGPH').innerHTML = gph.toFixed(3) + " GPH";
document.getElementById('resML').innerHTML = mlMin.toFixed(1) + " mL/min";
document.getElementById('resLbs').innerHTML = lbsPure.toFixed(3) + " lbs/day";
// Show result box
resultsArea.style.display = "block";
}