The Desalination Flow Requirements Estimator determines the feed-water flow needed to meet a daily desalinated product target at a selected recovery rate and operating schedule. It converts the product requirement into an average operating product flow, divides by recovery to obtain feed flow, and applies an optional design factor.
The calculation is especially relevant to desalination because a substantial part of feed may leave as concentrate rather than product water. Lower recovery therefore raises intake and pretreatment flow for the same product target. This estimator can support screening of intake, pretreatment, high-pressure feed, and concentrate-flow requirements, but it does not calculate pressure, osmotic conditions, membrane flux, temperature correction, pump head, or equipment redundancy.
Feed-flow requirement
gal/day
%
hr/day
×
Result
—
Required desalination feed flow
Average product flow—
Base feed flow—
Concentrate flow—
1. Enter the daily product target Use the required desalinated product-water volume per day.
2. Enter expected recovery Provide the fraction of feed water converted to product water.
3. Set effective operating hours Reflect the hours per day when the desalination train is producing at the modeled rate.
4. Apply a design factor Add explicit flow margin if the preliminary design should exceed the calculated base feed flow.
5. Review feed and concentrate flows Use the result for screening and compare it with the implied concentrate flow from the simple balance.
Product volume: desalinated product water in gallons per day
Operating hours: effective production hours per day
Recovery fraction: recovery percentage divided by 100
Design factor: dimensionless margin applied to base feed flow
Assumption: The calculation assumes steady production while operating and a simple feed = product + concentrate balance. Detailed desalination design requires additional hydraulic and process constraints.
What the result means
The main result is a planning estimate derived directly from the entered operating assumptions and should be interpreted within the stated system boundary.
Use project-specific design criteria, equipment data, and applicable requirements before making final engineering or procurement decisions.
Before the design factor, the simple balance implies about 370.4 gpm of concentrate flow during operation.
Why is desalination feed flow much higher than product flow at low recovery?
Only the recovery fraction of feed becomes product. At 45% recovery, for example, more than half of the incoming flow remains in the concentrate-side balance.
Should I use average or peak daily product demand?
Enter the daily product target that matches your planning case. If you already enter a peak-day target, avoid adding an overlapping design factor without a clear reason.
Does concentrate flow include pretreatment waste?
No. The displayed concentrate flow is simply base feed minus product. Pretreatment backwash, filter waste, chemical cleaning, and other side streams need separate accounting.
Can operating time be less than 24 hours?
Yes. Use effective production time after planned downtime, cleaning, or scheduling constraints; shorter operation increases required instantaneous flow.
Is this enough to size an intake pipe?
No. The result provides a flow basis, but intake design also depends on velocity limits, headloss, screens, environmental constraints, redundancy, and site hydraulics.