- Read pump curves at the installed head.
- Measure flow and nominal turnover with correct units.
- Verify branch balance and gravity return.
Delivered-flow calculator
Flow L/h = collected litres ÷ seconds × 3,600. Nominal turnovers/h = flow ÷ volume.
Use installed delivery at the normal head. Turnover arithmetic does not verify oxygen, uniform mixing or treatment capacity.
01 / Lift and resistance determine delivery
A pump’s maximum flow is usually quoted at little or no lift; its shutoff head is where flow falls to zero. Neither number alone describes the installed result. Static lift, pipe friction, fittings, filters and emitter pressure determine the operating point.
Use the manufacturer’s curve at the required total head and include changes as filters load or reservoir levels fall. Air pumps have a similar need for depth and backpressure information. Keep service access and replacement compatibility in the selection.
Reading: Hydroponics (HLA-6442) ↗ · Aquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
02 / Measure the actual outlet
Collect water for a timed interval at the real delivery point using a method that preserves the normal operating head as closely as possible. Flow in L/hour = collected litres ÷ seconds × 3,600. Collecting 2 L in 20 seconds equals 360 L/hour.
At 360 L/hour through an example 120 L inventory, the arithmetic is three nominal inventory turnovers per hour. This does not prove uniform mixing, oxygen delivery or biological filtration capacity; some water can short-circuit while other zones remain poorly exchanged.
- Record pump model, elevation difference, pipe layout, valve positions and filter condition.
- Run at the normal water level and measure outlet volume over a reliable timed interval.
- Repeat and compare measurements; use a larger sample if timing uncertainty is large.
- Measure each parallel branch rather than assuming equal division.
- Verify low-level operation, shutdown drain-back and restart after the installed flow is acceptable.
03 / Balance the branches
A split manifold does not guarantee equal flow. Different branch lengths, fittings, emitters and root obstruction change resistance. Use accessible balancing valves where appropriate and record the working positions.
If one branch under-delivers, inspect its obstruction and pressure requirement before increasing the whole pump. Increasing flow can overload a return line that was already near capacity. Confirm gravity drainage independently.
Reading: Irrigation in Hydroponic Systems ↗
04 / Keep the measured baseline
Record clean-system delivery and the point at which declining flow calls for service. Inspect screens, filters and impellers according to their manufacturers. De-energize and isolate before opening equipment.
After replacement, repeat the measurement even if the new pump carries the same label. Parts, plumbing and operating levels can differ. Keep a spare strategy appropriate to the root or fish system’s outage tolerance.
FIELD QUESTIONDoes three turnovers per hour mean every litre passes through the filter three times?
No. It is total flow divided by inventory. Mixing patterns and short-circuiting determine the paths of individual water parcels.
Parts & buying criteria
Showing nutrient film technique. Quantities describe the teaching model. Specify real working volume, support, fittings and instruments for your installation.
01Reservoir1 · illustrated quantity+
Holds the recirculating nutrient solution. This is the common sampling and refill point for both channels.
Inspect: In cutaway view, compare the water surface with the pump intake. The drawing leaves room above the water; it does not specify a working volume.
Maintain: Record the level before adding water. Inspect the cover, clean accessible deposits and keep the intake submerged during use.
Opaque, cleanable container rated by its manufacturer for the intended use; accessible lid and drain.
Supplier links can be added by the publisher. The criteria stand independently.02Pump & supply1 · illustrated quantity+
Lifts solution from the reservoir to the channel inlets. Cyan packets indicate the direction of delivery.
Inspect: Follow the rising supply pipe and its branch to each channel. Both inlets need an observable supply.
Maintain: Disconnect power before opening the pump. Inspect its inlet screen and confirm both branches flow after reassembly.
Compare the pump curve at the installed lift and pipe resistance; include service access and replacement availability.
Supplier links can be added by the publisher. The criteria stand independently.03Growing channels1 · illustrated quantity+
Contain the shallow stream beneath the plants and guide it toward the return.
Inspect: Open the cutaway to find the channel floor beneath the roots. The slope is exaggerated for reading.
Maintain: Look along each channel for ponding, debris or an obstructing root mat; inspect the outlet before changing the pump.
Removable covers, supported slope, smooth cleanable surfaces and outlets accessible with plants in place.
Supplier links can be added by the publisher. The criteria stand independently.04Plant baskets6 illustrated · illustrated quantity+
Bridge the opening in the channel cover while allowing roots to pass through.
Inspect: In exploded view, the baskets lift above the channels. The open slats reveal the relationship between support and roots.
Maintain: Check that each rim sits securely and that roots are not pinched at transplanting or inspection.
Match the basket rim and hole diameter; allow removal without damaging adjacent plants.
Supplier links can be added by the publisher. The criteria stand independently.05Support mediumFor 6 baskets · illustrated quantity+
The illustrated expanded clay supports the seedling in its basket. The channels are not filled with aggregate.
Inspect: Select the brown pebbles and separate the basket in exploded view. Media texture is simplified.
Maintain: Remove loose particles before installation. Inspect whether the starter plug stays appropriately moist.
Select a stable grade that stays in the basket; compare water retention, dust and cleaning requirements.
Supplier links can be added by the publisher. The criteria stand independently.06Gravity return1 · illustrated quantity+
Collects channel outflow and brings it back to the reservoir without a second pump.
Inspect: Trace the low ends of both channels into the common return. Inspect the full path before assuming the circuit is clear.
Maintain: Remove obstructions and check for leaks. Test drainage with the pump off during commissioning.
Removable unions, supported pipe and sufficient drain capacity under the actual installation conditions.
Supplier links can be added by the publisher. The criteria stand independently.Evidence beside the lesson.
Source checks: September 2026. The geometry, inspection exercises and worksheets are original teaching material. The named organizations have not endorsed or reviewed this site.
Published recipe rates and planning ranges retain their source context. Calculator equations are accounting tools; they do not predict uptake, yield, toxicity or safe stocking. Model dimensions, water speeds, roots and fish counts are illustrative. Verify species, crop, source water and product labels for a real system.
- Oklahoma State University ExtensionHydroponics (HLA-6442) ↗
System categories and recirculating nutrient delivery.
- Southern Regional Aquaculture Center · hosted by OSU ExtensionAquaponics—Integrating Fish and Plant Culture (SRAC 454) ↗
Tank-to-treatment-to-growing-to-sump layout and production tradeoffs.
- University of Kentucky Center for Crop DiversificationIrrigation in Hydroponic Systems ↗
Media irrigation and delivery management.
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