Total System Flow Calculator

Calculator Inputs

Output unit L/min L/hour US GPM

Pump rating is assumed in this same unit.

Reserve capacity (%)

Covers pressure variation, clogging, aging, and minor leaks.

Future expansion (%)

Allows extra beds, added zones, or greenhouse upgrades.

Pump rating (optional)

Used to flag undersized or limited capacity.

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Flow Components

Add rows for emitters, heads, taps, or recirculation loops.

Add row Reset example rows

Component name	Qty	Flow / unit	Unit	Simultaneous (%)	Remove
			L/min L/hour GPM		X
			L/min L/hour GPM		X
			L/min L/hour GPM		X
			L/min L/hour GPM		X

Submit Clear

Formula Used

Each component contributes flow based on quantity, flow per unit, and how much of it runs at the same time.

• ComponentFlow = Quantity × FlowPerUnit × (Simultaneous% ÷ 100)
• PeakFlow = Σ ComponentFlow
• RecommendedFlow = PeakFlow × (1 + Reserve%/100) × (1 + Expansion%/100)

Tip: For zone-based schedules, set Simultaneous% to 0 for zones that never overlap.

How to Use This Calculator

1. Choose an output unit that matches your pump label.
2. Add each water-using component as one row.
3. Enter quantity and flow per unit from specs.
4. Set simultaneity to reflect your real schedule.
5. Use reserve and expansion to reduce surprises.
6. Press Submit and review peak and recommended flow.

Irrigation Demand and Flow Baselines

Total system flow is the instantaneous water demand when selected components operate together. In practice, gardens mix drip, micro-spray, and sprinklers, each with different ratings and pressure needs. This calculator standardizes every row into a common flow basis before summing contributions. Use manufacturer flow figures at the intended operating pressure, then confirm output with a bucket-and-timer field test to reduce surprises.

Unit Handling and Conversion Discipline

Emitters often publish liters per hour, while taps and pumps are labeled in liters per minute or gallons per minute. Converting everything into one unit prevents hidden sizing errors, especially when comparing zones. The tool converts L/hour and GPM into a single internal baseline, then reports in your chosen unit. Keep the pump unit consistent with the selected output unit to compare ratings correctly.

Simultaneity, Zoning, and Scheduling Logic

Simultaneity reflects how much of a component runs at the same time. A value of 100% means always on during the run window, while 0% means the zone never overlaps with your peak scenario. For timer-based irrigation, model the worst-case overlap: back-to-back zones use low simultaneity across zones, but hand watering and recirculation may overlap and increase peak demand.

Reserve and Expansion Factors

Reserve capacity adds margin for filter loading, minor leaks, valve wear, and pressure variation from supply lines. Expansion accounts for future beds, extra laterals, or greenhouse upgrades. Applying both factors to peak flow yields a recommended pump flow that is more resilient than sizing to the bare peak. If your supply is fixed, use these factors to refine scheduling instead of oversizing hardware.

Using Results for Pump and Pipe Decisions

Peak flow supports immediate “can it run?” checks, while recommended flow guides pump selection and mainline sizing. If the pump rating is below the recommended flow, reduce overlap, split zones, or upgrade the pump. If peak is high but recommended is acceptable, adjust simultaneity to match real operation. Pair this output with pressure-loss checks to validate pipe diameters and keep emitters within their pressure range. Record seasonal changes, because demand and overlap patterns shift.

FAQs

1) What does “peak simultaneous flow” represent?

It is the summed flow of every component after applying quantity and simultaneity. It models the maximum demand you expect during an overlap window, not the total daily water use.

2) How should I set simultaneity for irrigation zones?

Use 100% for items that run together in the same program window. Use 0% for zones that never overlap with your peak case. For partial overlap, estimate the percentage of time they run together.

3) Why include reserve capacity?

Reserve provides breathing room for clogged filters, aging emitters, slight pressure drops, and minor leaks. It helps maintain consistent distribution without constantly operating at the edge of system capacity.

4) Should I size the pump to peak or recommended flow?

Use recommended flow for pump selection when possible because it includes margin. If supply or budget is fixed, keep the pump near peak and reduce overlaps by splitting zones or adjusting schedules.

5) Are the GPM conversions US or imperial?

The calculator uses US gallons per minute for conversion. If your equipment is labeled in imperial gallons, convert those values to US GPM first to avoid underestimating flow.

6) Can I use this for recirculating hydroponic loops?

Yes. Add pumps, returns, filters, and outlets as components, then set simultaneity based on how the loop operates. Verify the measured flow with a flow meter or timed container test for accuracy.