Flow Measurement · Free Calculator
Chemical Dosing Pump Calculator
Find how much chemical solution to dose into a water or process flow to reach a target concentration, and the dosing pump stroke or speed setting.
Dose rateppm (mg/L)Pump settingWater treatment
mg/L (ppm)
% w/w
kg/L
L/h
L
Dosing rate0.6667 L/h
Pump setting16.7 % of maximum
Active chemical used0.1 kg/h
Solution used per day16 L
Day tank lasts12.5 days
How this result was calculated
- Active chemical = Q × dose = 50 m³/h × 2 g/m³ = 100 g/h
- Solution = active ÷ strength = 0.8 kg/h
- Dosing rate = solution ÷ density = 0.6667 L/h
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Dosing Formulas
Active chemical (g/h) = Q (m³/h) × dose (mg/L = g/m³)
Dosing rate (L/h) = active ÷ (strength ÷ 100) ÷ density (g/L)
Pump setting (%) = dosing rate ÷ pump maximum × 100
Dosing rate (L/h) = active ÷ (strength ÷ 100) ÷ density (g/L)
Pump setting (%) = dosing rate ÷ pump maximum × 100
Q is the treated flow, the dose is the target concentration of active chemical, strength the active content of the solution by mass (for example 12.5 % sodium hypochlorite) and density the solution density. For flow paced dosing, the pump follows a flow meter signal so the dose stays constant as flow changes.
Worked example
Dosing 2 mg/L of chlorine into 50 m³/h using 12.5 % hypochlorite (1.2 kg/L) needs 100 g/h of active chlorine, which is 0.67 L/h of solution, about 17 % of a 4 L/h pump.
Key insight: flow paced control using a 4 to 20 mA or pulse signal from the flow meter keeps the dose constant; a fixed pump setting overdoses at low flow and underdoses at high flow.
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Frequently Asked Questions
Is ppm the same as mg/L?
For water and dilute solutions, yes: 1 mg/L ≈ 1 ppm by mass.
Why does chemical strength matter?
Commercial chemicals are solutions; only the active part treats the water, so the dosing rate must be scaled by strength.
How do I set a dosing pump?
Set the stroke length and speed (or the speed of a motor driven pump) to deliver the calculated L/h, then verify with a calibration column.
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