Disinfection

Chlorine dose

Chlorine dose and sodium hypochlorite feed rate from demand, target residual and flow.

Hypochlorite solution—L/h

Chlorine dose—mg/L

Available chlorine—kg/day

Hypochlorite solution—L/day

Formula

Dose = demand + residual
Cl₂ (g/h) = dose (mg/L) × Q (m³/h)
Strength (g/L) = trade % × 10
Solution (L/h) = Cl₂ (g/h) / strength (g/L)

Sources

AWWA Ohio Section, White Paper on Disinfection with Hypochlorites (2007)
Dosage equation (section 2.5.2) and definition of trade percent: 200 g/L available chlorine is 20 trade percent. Metric form of the same equations. The paper cites AWWA B300-04; the current edition of the hypochlorite standard is ANSI/AWWA B300-24.

Limits and assumptions

Find the chlorine demand by a jar test on your water. It changes with temperature, organics and contact time (AWWA Ohio 2007, section 2.2).
Sodium hypochlorite loses available chlorine in storage, faster with heat and light. Use the measured strength, not the delivery note (AWWA Ohio 2007, section 2.4).
Trade percent means grams of available chlorine per 100 mL. If your supplier gives percent by weight, convert with the solution density.
Required residual and contact time are set by your local regulations. They are not built into this calculator.