Water Treatment Chemical Concentrations Reference

This guide consolidates concentration and specific gravity (S.G.) data for chemicals routinely used in drinking water treatment: sodium hypochlorite, alum, ferric chloride, ferric sulfate, sodium permanganate, sodium hydroxide, and ammonium sulfate. Specific gravity is the ratio of solution density to pure water and is essential for converting between volume-based pump settings (GPD or mL/min) and mass-based dosage targets (lb/day or mg/L). Always verify values against the current Safety Data Sheet or supplier certificate of analysis before performing compliance-critical calculations.

Key unit conversions are provided: 1 gallon = 8.34 lb (water at 60°F), 1 mg/L = 1 ppm, and % concentration × 10,000 = mg/L. To find chemical weight from volume, multiply gallons × 8.34 × S.G. × concentration (decimal). To find required pump volume from a dosage target, divide the chemical dose by (8.34 × S.G. × concentration).

Several chemicals vary in form or concentration by supplier. Sodium hypochlorite degrades over 30–60 days in storage and should be verified by certificate of analysis, not label. Ferric chloride comes in 35% and 42% grades with different specific gravities; switching grades requires recalibration. Sodium hydroxide (50% grade) is viscous and may need heat tracing in cold climates. Aluminum sulfate concentration and form vary by supplier. Always consult your state primacy agency and design engineer before implementing chloramine disinfection systems.