Dosing Pump Flow Rate Calculation

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Dosing Pump Calibration Calculator
Flow Rate (mL/min): –
Flow Rate (Liters/hour): –
Flow Rate (Gallons/hour): –
Daily Output (Gallons/day): –

How to Calculate Dosing Pump Flow Rate

Accurate chemical dosing is critical for water treatment, industrial processing, and agricultural applications. Over time, dosing pump diaphragms wear out, check valves clog, and viscosity changes due to temperature, all of which alter the actual output of the pump. To ensure precise dosing, a Drawdown Calibration Test is required.

The Drawdown Calibration Method

This calculator uses the drawdown method, which is the industry standard for calibrating metering pumps. The process involves measuring exactly how much liquid the pump draws from a calibration column (a graduated cylinder) over a specific period of time.

To perform the test:

  • Isolate the pump suction line so it draws from the calibration column instead of the main tank.
  • Fill the calibration column with the chemical to be dosed.
  • Run the pump for a set duration (typically 30 or 60 seconds).
  • Record the volume of liquid removed (drawn down) from the column in milliliters (mL).
  • Input the volume and time into the calculator above.

Formulas Used

Understanding the math behind the flow rate calculation allows for manual verification. The fundamental formula is Volume divided by Time, normalized to standard units.

mL/min = (Drawdown Volume mL ÷ Duration seconds) × 60
L/hr = (mL/min × 60) ÷ 1000
GPH (US) = L/hr × 0.264172

Example Calculation

Suppose you are calibrating a sodium hypochlorite pump. You fill the calibration column and run the pump at 80% speed for exactly 30 seconds. The liquid level drops by 45 mL.

Step 1: Calculate mL/min
(45 mL ÷ 30 sec) × 60 = 90 mL/min

Step 2: Convert to Liters per Hour
(90 × 60) ÷ 1000 = 5.4 L/hr

If your target dosage requires 6.0 L/hr, this test indicates the pump is under-dosing, and you must increase the stroke length or frequency setting.

Why Calibration is Necessary

Relying solely on the pump's manual dial or digital percentage display is often inaccurate. Factors such as back pressure in the discharge line and the viscosity of the chemical can significantly reduce flow rates compared to the manufacturer's rating (which is usually tested with water at zero pressure).

function calculateDosingFlow() { // 1. Get input values using var var volumeInput = document.getElementById('drawdownVolume'); var timeInput = document.getElementById('testDuration'); var resultBox = document.getElementById('dosingResults'); // 2. Parse values var volume = parseFloat(volumeInput.value); var duration = parseFloat(timeInput.value); // 3. Validation if (isNaN(volume) || isNaN(duration) || duration <= 0 || volume < 0) { alert("Please enter valid positive numbers for volume and duration."); resultBox.style.display = 'none'; return; } // 4. Calculations // Calculate Milliliters per Minute var mlPerMin = (volume / duration) * 60; // Calculate Liters per Hour var lPerHr = (mlPerMin * 60) / 1000; // Calculate Gallons per Hour (US Gallons) var gph = lPerHr * 0.264172; // Calculate Gallons per Day var gpd = gph * 24; // 5. Update UI document.getElementById('resMlMin').innerHTML = mlPerMin.toFixed(2) + " mL/min"; document.getElementById('resLHr').innerHTML = lPerHr.toFixed(3) + " L/hr"; document.getElementById('resGPH').innerHTML = gph.toFixed(3) + " GPH"; document.getElementById('resGPD').innerHTML = gpd.toFixed(2) + " GPD"; // Show results resultBox.style.display = 'block'; }

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