Free Engineering Tools

Water Treatment Dosing CalculatorsInline · Cooling Tower · RO · Boiler · Biocide

Five free calculators for plant engineers: continuous chemical dosing, cooling tower blowdown and makeup, RO antiscalant, boiler oxygen scavenger and biocide slug dosing. Each shows its formula so you can check the maths. Results update instantly as you type.

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Core Formula

kg/day= m³/h × 24 × ppm ÷ 1000

E= 0.00153 × R × ΔT

B= E ÷ (CoC − 1)

Na₂SO₃≈ 7.88 × ppm O₂

MODULE 01

Continuous Flow-Proportional Dosing

Daily chemical requirement and metering-pump rate for continuous inline dosing.

System flow rate (m³/h)

Active dosage (ppm)

Product active content (%)

Specific gravity (g/cm³)

Operating hours per day (h)

Active chemical / day0 kg

Product required / day0 kg

Product volume / day0 L

Metering pump rate0 L/h

Product / month (30 d)0 kg

Active (kg/day) = Q × h × ppm ÷ 1000
Product = Active ÷ (active % ÷ 100)
Volume = Product ÷ SG · Pump = Volume ÷ h

MODULE 02

Cooling Tower Evaporation, Blowdown & Inhibitor Dosing

Cooling tower mass balance from recirculation rate, temperature drop and cycles of concentration (CoC).

Recirculation flow (m³/h)

Cooling range ΔT (°C)

Cycles of concentration (CoC)

Inhibitor dose in makeup (ppm)

Product active content (%)

Specific gravity (kg/L)

Evaporation loss0 m³/h

Blowdown0 m³/h

Makeup water0 m³/h

Inhibitor product / day0 kg

Inhibitor volume / day0 L

E = 0.00153 × R × ΔT · B = E ÷ (CoC − 1)
M = E + B (drift ignored)
Product (kg/day) = M × 24 × ppm ÷ 1000 ÷ active%

MODULE 03

Reverse Osmosis (RO) Antiscalant Dosing

Neat antiscalant consumption for your RO feed flow.

RO feed water flow (m³/h)

Antiscalant dose (as product) (ppm)

Antiscalant feed rate0 kg/h

Antiscalant / day0 kg

Antiscalant / month (30 d)0 kg

Feed (kg/h) = Q (m³/h) × ppm ÷ 1000
Daily = Feed × 24

MODULE 04

Boiler Oxygen Scavenger & Scale Inhibitor Dosing

Feedwater demand, theoretical sodium sulfite demand and scale-inhibitor feed for steam boilers.

Steam generation (t/h)

Continuous blowdown (%)

Dissolved O₂ in feedwater (ppm)

Safety factor (1.2–1.5)

Scale inhibitor in feed (ppm)

Polymer product concentration (%)

Feedwater demand0 t/h

Blowdown flow0 t/h

Sodium sulfite (100%) / day0 kg

Scale inhibitor product / day0 kg

F = Steam ÷ (1 − BD%) · Blowdown = F − Steam
Na₂SO₃ = F × 24 × O₂ × 7.88 × SF ÷ 1000
Inhibitor = F × 24 × ppm ÷ 1000 ÷ conc%

MODULE 05

Biocide Shock / Slug Dosing

One-time slug dose for microbial and bio-slime knockdown in cooling towers or closed loops.

Total system water volume (m³)

Target slug concentration (ppm)

Product active content (%)

Specific gravity (g/cm³)

Active biocide required0 kg

Product per slug0 kg

Product volume per slug0 L

Active (kg) = V (m³) × ppm ÷ 1000
Product = Active ÷ active% · Volume = Product ÷ SG

These calculators give estimates based on ideal steady-state conditions. Confirm final dosing with jar testing or our technical chemists.

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FAQ

Frequently Asked Questions

How do I calculate chemical dosage for water treatment?

Product required (kg/day) = flow (m³/h) × 24 × dose (ppm) ÷ 1000 ÷ (product active % ÷ 100). For example, 100 m³/h at 10 ppm active using a 50% product needs 48 kg/day.

How do I calculate cooling tower evaporation and blowdown?

Evaporation (m³/h) ≈ 0.00153 × recirculation (m³/h) × ΔT (°C). Blowdown = evaporation ÷ (cycles of concentration − 1), and makeup = evaporation + blowdown (drift ignored).

How much sodium sulfite is needed to remove dissolved oxygen?

Theoretically 7.88 ppm of sodium sulfite per 1 ppm of dissolved oxygen, multiplied by a safety factor of about 1.2–1.5 for excess residual.

How is a biocide slug dose calculated?

Active biocide (kg) = system volume (m³) × target ppm ÷ 1000. Divide by the product's active fraction to get the product quantity.