Calculate RO antiscalant pump feed rate, daily product use, and chemical cost from your system flow, dose, mixing strength, and price.
Table of contents
How to use our RO Antiscalant Dose and Pump Rate Calculator
- Enter the RO feed-water flow while the system is running, not the permeate or product-water flow.
- Enter RO run time as the average hours the system actually operates each day.
- Copy the Prescribed antiscalant dose and Antiscalant product density from the approved design report or product sheet, then choose the printed density unit.
- Enter Antiscalant product in pump solution as 100 for neat product, or the product share of a diluted day-tank solution, then enter Antiscalant price per gallon.
- Click Calculate and compare the pump feed rate with the metering pump's approved calibration result; the calculated rate applies only while the RO is running.
Definitions
RO feed-water flow: Water entering the reverse osmosis system while it is operating. It is not the permeate flow.
Prescribed antiscalant dose: The mass of neat commercial antiscalant added per liter of feed water, stated in mg/L.
Neat antiscalant: Commercial product before dilution water is added.
Pump solution: The neat product or diluted liquid that the metering pump delivers to the RO feed water.
Product density: Product mass per unit volume. It converts the required product mass into gallons of neat product.
Percent by volume: The fraction of final pump-solution volume made up by antiscalant product. A 20% solution contains 20% product by volume.
mL/min: Milliliters per minute. This is the metering-pump setting while the RO system runs.
Common mistakes and quick fixes
Mistake: Entering permeate flow instead of RO feed-water flow.
Fix: Use the water flow entering the RO system while it runs.
Mistake: Using 24 for RO run time when the system runs only part of the day.
Fix: Enter the actual average operating hours per day; Pump feed rate while the RO is running remains a while-running setting.
Mistake: Entering the percent of water instead of Antiscalant product in pump solution.
Fix: Enter the percent of final solution that is commercial antiscalant product. Use 100 for neat product.
Mistake: Typing a lb/gal density while Product density unit is set to kg/L or g/mL.
Fix: Choose the unit shown on the product sheet before entering Antiscalant product density.
Mistake: Using a diluted day-tank cost for Antiscalant price.
Fix: Enter the price per gallon of neat commercial product so Antiscalant product cost per day is comparable to invoices.
Mistake: Entering flow as 1,01.
Fix: Check RO feed-water flow and then recalculate. Use commas only for thousands separators, such as 1,000, and use a decimal point for decimals.
Limitations & Key Assumptions / Boundary Conditions
- The calculator uses the prescribed antiscalant dose you enter. It does not select a product or determine a safe dose.
- Pump feed rate applies while RO feed water is flowing. It is not a 24-hour average when RO run time is less than 24 hours.
- Results depend on actual feed-water flow, product density, day-tank mixing percentage, and pump calibration. Verify the real pump output using the site's approved procedure.
- Chemical cost includes only neat antiscalant volume times Antiscalant price. It excludes dilution water, delivery, taxes, labor, equipment, maintenance, and disposal.
- The 30-day cost is daily product cost multiplied by 30. It is a comparison period, not a calendar-month forecast.
- A zero RO feed-water flow correctly produces zero chemical use and cost, even if the other entries are nonzero.
Methodology
Calculation method
The calculator first converts density to kg/L when lb/gal is selected. It uses 0.45359237 kg per lb and 3.785411784 L per US gallon. These are standard unit conversions. [1]
Feed water per day (gal/day) = RO feed-water flow (gpm) x 60 x RO run time (hours/day)
The dose is applied to feed-water volume, then density converts required product mass into neat product volume. The liter-per-gallon factors cancel because both water and product use the same US gallon definition.
Neat product (gal/day) = feed water per day x prescribed dose (mg/L) / [density (kg/L) x 1,000,000]
Pump solution (gal/day) = neat product (gal/day) / [product in pump solution (%) / 100]
Pump feed rate (mL/min) = pump solution (gal/day) x 3,785.411784 / [RO run time (hours/day) x 60]
Product cost per day ($/day) = neat product (gal/day) x antiscalant price ($/gal)
Product cost for 30 days ($) = product cost per day x 30
Worked example
With 500 gpm of feed water, 24 hours per day, a 3 mg/L dose, 1.1 kg/L density, 100% product in the pump solution, and $25 per gallon, the calculator gives 720,000 gal/day of feed water, 1.9636 gal/day of neat product, a 5.1619 mL/min pump rate, and about $49.09 per day.