Inputs
Enter your nozzle rating, count, pressure, and schedule. The calculator estimates corrected flow, daily water use, and reservoir sizing.
Formula used
- Q₂ = Q₁ × (P₂ / P₁)ⁿ — correct one-nozzle flow for pressure.
- Q_total = Q₂ × N — multiply by nozzle count.
- V_day = Q_total × (t/60) × (duty/100) — daily volume.
- V_day,loss = V_day × (1 + loss/100) — add allowance.
- Tank = V_day,loss × days — reservoir sizing.
How to use this calculator
- Find your nozzle rated output and rated pressure from the datasheet.
- Measure or estimate actual pressure at the fogging line while running.
- Enter nozzle count, runtime minutes per day, and your duty cycle.
- Add a small loss allowance for purge cycles and overspray.
- Use the reservoir sizing result to pick a tank with spare headroom.
Example data table
| Nozzle rating | Nozzles | Rated pressure | Actual pressure | Runtime | Duty | Loss | Total flow (L/h) | Daily use incl. loss (L/day) | Tank for 3 days (L) |
|---|---|---|---|---|---|---|---|---|---|
| 120 mL/min | 12 | 3 bar | 3.5 bar | 45 min/day | 60% | 5% | 99.48 | 47.09 | 141.27 |
Numbers are illustrative; your nozzle design and filtration affect real output.
Operational flow planning for consistent mist
Fogger performance depends on stable pressure at the nozzle tips. The calculator converts rated nozzle output to an expected running output using the pressure ratio and exponent. This helps you estimate the real demand on the pump and avoid undersizing that causes weak mist, uneven coverage, and longer recovery times after ventilation.
Pressure, filtration, and nozzle loading
A small pressure drop across filters and long tubing can reduce output significantly because flow scales with pressure. Keep filtration appropriate for nozzle orifice size, maintain clean water, and reduce sharp fittings. If you increase nozzle count, confirm the pump can still hold target pressure at the calculated total flow.
Scheduling with runtime and duty cycle
Many growers pulse foggers to manage leaf wetness and humidity spikes. Use the runtime and duty cycle fields to model pulsing. For example, 60% duty within 45 minutes means the system sprays for 27 minutes total. This improves water planning and makes reservoir sizing more realistic for daily operation.
Reservoir sizing and loss allowance
The loss allowance accounts for purge cycles, overspray drift, and minor leaks. In enclosed benches, 3–8% is common; in open structures or windy conditions, it can be higher. The suggested tank volume multiplies the loss-adjusted daily use by your target days, then you can add extra headroom for cleaning and sediment.
Example scenario data for quick validation
Example inputs: nozzle rating 120 mL/min at 3 bar, 12 nozzles, actual pressure 3.5 bar, exponent 0.5, runtime 45 minutes/day, duty 60%, loss 5%, coverage 3 days. Example outputs: total flow about 99.48 L/h, daily use with loss about 47.09 L/day, and a tank near 141.27 L for three days. Use these values to verify your setup.
FAQs
1) What does the pressure exponent mean?
It describes how nozzle flow changes with pressure. Many orifice-style nozzles follow an approximate square-root relationship, so n is often near 0.5. Use your nozzle datasheet if a different exponent is provided.
2) Should I use pump pressure or line pressure?
Use pressure at the fogging line, near the nozzles. Pump outlet pressure can be higher due to tubing and filter losses, which would overestimate output if used directly.
3) Why include duty cycle if I already enter runtime?
Runtime is the scheduled window, while duty cycle represents on-time within that window. Pulsing reduces total spray time, which lowers daily water use and can help control leaf wetness.
4) How do I choose the loss allowance?
Start with 5% for well-sealed indoor systems. Increase it if you purge lines often, fog into open air, or notice drift and leaks. The allowance helps keep reservoir estimates conservative.
5) My calculated flow is high. What should I check?
Confirm nozzle rating units, nozzle count, and pressure values. Ensure both pressures share the same unit. Also verify filtration and tubing aren’t causing large losses that reduce actual line pressure.
6) Can I use this for multiple zones?
Yes. Calculate each zone separately using its nozzle count and line pressure, then sum daily water use to size a shared reservoir. This also helps you evaluate staged schedules across zones.
7) Does water temperature change the result?
Slightly. Viscosity and density change with temperature, but the effect is usually small compared with pressure variation and clogging. For precision work, validate output by measuring refill volume over time.