Fluoride Dose & Feed Rate Calculator
Water fluoridation feed rates for operators: pick your fluoride chemical, enter flow and target dose, and get the daily feed rate — with adjustable purity and strength.
How the calculation works
The calculator converts your flow to MGD, subtracts background fluoride from the target to get the dose to apply, converts that dose to pounds of fluoride per day with the 8.34 factor, and then converts to the amount of the chemical you selected.
Flow conversion: MGD = gpm × 1,440 ÷ 1,000,000
Dose to apply: dose (mg/L) = max(0, target − background)
Fluoride required: F (lb/day) = 8.34 × MGD × dose
Dry chemicals: chemical (lb/day) = F ÷ (F fraction × purity ÷ 100), where the available-F fractions are 0.452 for NaF and 0.607 for Na2SiF6.
Fluorosilicic acid: the strength % entered is the %F. F per gal (lb/gal) = SG × 8.34 × (strength ÷ 100), then acid (gal/day) = F ÷ F per gal and acid (lb/day) = gal/day × SG × 8.34.
Notes & limitations
- The US HHS recommends 0.7 mg/L fluoride for community water systems; dosing must follow your state primacy-agency requirements.
- Fluoride chemicals are toxic in concentrated form — handle with proper PPE (especially fluorosilicic acid, which is corrosive), follow the SDS, and store dry chemicals in a dry location.
- Verify feeder calibration in the field with a drawdown test; the calculated rate is a starting setpoint, not a substitute for feed-rate verification.
- Available-F fractions (0.452, 0.607) and default strengths are typical values — use the assay on your chemical’s certificate of analysis when available.
Reference: US HHS recommendation for community water fluoridation (0.7 mg/L); AWWA Manual M4, Water Fluoridation Principles and Practices.
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