How to use this calculator
- Enter water flow. Use the design flow through the treated pipe or process stream.
- Enter active dose. Use the desired mg/L dose as active ingredient.
- Enter product data. Set chemical strength by mass and product specific gravity from the supplier data sheet.
- Set pump and tank. Enter rated pump capacity at pressure and usable day-tank volume.
- Review output. Check L/h, mL/min, gpd, pump percent setting and tank runtime.
How it works
For dilute water treatment, target dose is usually entered as
D = mg/L active ingredient
and 1 mg/L is treated as approximately 1 ppm. Active
mass flow is:
m_active = Q_water x D x 60 / 1,000,000
where water flow is in L/min and active mass flow is kg/h.
Product feed divides by active strength and product density:
Q_chem = m_active / (S x SG)
where S is active fraction by mass and SG is product
specific gravity in kg/L. The optional feed margin is applied to the target
dose before those calculations.
Pair the result with the pipe pressure drop calculator, pipe size calculator, orifice flow calculator and pump NPSH calculator when the injection point is part of a larger water or process piping system. For hardness treatment, use the water softener sizing calculator to estimate grain capacity, resin volume and regeneration interval.
Worked example
Verified against the live calculator
A 100 L/min water line needs 2 mg/L active dose from
a 10% product with SG = 1.0 and no margin. Active demand
is 0.012 kg/h, product mass flow is 0.12 kg/h, and the
product feed is 0.12 L/h, or 2.0 mL/min. A
1.2 L/h pump would run at about 10% of rated output.
Frequently asked questions
How do you calculate chemical feed rate for ppm dosing?
For dilute water treatment, 1 mg/L is approximately 1 ppm. Active mass per hour is water flow in L/min times dose in mg/L times 60, divided by 1,000,000. Divide by active strength and specific gravity to get product feed in L/h.
Is the dose entered as active ingredient or purchased product?
This calculator treats target dose as active ingredient. For example, a 2 mg/L chlorine dose with 12.5% sodium hypochlorite divides the active demand by 0.125.
How is the pump setting calculated?
Pump setting is required product feed divided by rated pump capacity. Use the pump capacity at the operating pressure, not the catalog open-discharge number.
Does this replace a calibration drawdown test?
No. Use this as a starting setpoint, then verify actual output with a drawdown column, flow check, analyzer feedback and the site operating procedure.
Method & assumptions
- Target dose is treated as active ingredient in mg/L; convert product-dose conventions before entering data.
- Specific gravity is used as kg/L for aqueous products; use supplier data at operating temperature.
- Pump capacity should be the usable metering output at discharge pressure and stroke/speed limits.
- This calculator does not check chemical compatibility, injector pressure, backpressure valves, anti-siphon devices, dilution, reaction demand, residual control, hazardous materials, codes or safety procedures.