Calculator Inputs
Example Data Table
| Scenario | Area | Demand | Efficiency | Zones | Hours/day | Reserve |
|---|---|---|---|---|---|---|
| Irrigation | 120 m² | 6 mm/day | 0.85 | 3 | 1.2 | 2 days |
| Greenhouse | 800 ft² | 0.20 in/day | 0.90 | 2 | 1.0 | 1.5 days |
| Hydroponics | 60 m² | 4 mm/day | 0.92 | 2 | 1.0 | 1 day |
Formula Used
1) Daily demand: Liters/day = Area(m²) × Demand(mm/day). One millimeter over one square meter equals one liter.
2) Rain offset: Net demand = max(0, Demand − Rain credit).
3) Capacity with losses: Required = (Net ÷ Efficiency) × Peak factor.
4) Buffer: Required = Required × (1 + Buffer%/100).
5) Per-zone flow: If zones run sequentially, Per-zone liters = Required ÷ Zones, then Pump flow = Per-zone liters ÷ (Irrigation hours × 60).
6) Storage sizing: Storage = Required × Reserve days.
How to Use This Calculator
- Choose the scenario and unit system that match your garden.
- Enter the area and a realistic daily demand depth.
- Add a rain credit only if it reliably reduces watering.
- Set efficiency, zones, and irrigation hours to reflect operations.
- Use peak factor and buffer to cover hotter days and uncertainty.
- Set reserve days if you rely on a storage tank or intermittent supply.
- Optionally add emitter details to compare with your pump target.
- Press Calculate. Download CSV or PDF for your records.
System Capacity Planning Article
1) Daily Demand and Area Drivers
System capacity begins with daily water demand expressed as a depth. A demand of 5 mm/day over 100 m² equals about 500 L/day before losses. Crop type, canopy size, wind, and temperature can shift demand by 20–40% across seasons, so using conservative peak values improves reliability.
2) Efficiency, Losses, and Practical Targets
Irrigation efficiency accounts for evaporation, drift, leaks, and uneven distribution. A well-tuned drip layout may reach 0.85–0.95, while overhead sprinklers can be lower in windy sites. The calculator divides net demand by efficiency so the pump and supply target the delivered requirement, not the theoretical crop need. Regular filter maintenance and pressure regulation can improve efficiency without changing crop demand.
3) Zoning and Pump Flow Sizing
Zoning reduces the instantaneous flow requirement by running one zone at a time. For example, a 1,200 L/day requirement split into three zones and applied over 1.2 hours/day yields about 5.6 L/min per active zone. Shorter watering windows raise flow, while additional zones reduce it. If your schedule allows multiple cycles, you can distribute volume more evenly through the day.
4) Storage Reserve and Buffer Strategy
Storage supports outages and stabilizes supply pressure. A two‑day reserve on a 900 L/day system suggests roughly 1,800 L of usable storage. The buffer percentage adds an extra margin for measurement error, emitter clogging, and future expansion. Many teams apply 5–15% depending on site uncertainty. When sizing tanks, also consider float switch deadbands and unusable volume below outlets.
5) Emitter Checks and Hydroponics Circulation
Emitter flow provides a reality check against the pump target. If one zone has 60 emitters at 2 L/h, active-zone demand is about 2.0 L/min, indicating the pump can be sized near that value with head losses added separately. For hydroponics, turnover targets help maintain oxygenation and nutrient uniformity in the reservoir. A goal of four turnovers of a 200 L reservoir during a one-hour circulation window implies about 800 L/h of circulation capacity.
FAQs
1) What does “demand depth” represent?
It is a daily water depth over the irrigated area. One millimeter over one square meter equals one liter, so it converts climate and crop needs into volume.
2) How should I choose efficiency?
Use measured performance when available. Drip systems often fall between 0.85 and 0.95. If you suspect leaks, overspray, or uneven wetting, choose a lower value to stay conservative.
3) Does the pump flow include pressure losses?
No. The per-zone flow is a volume rate target. Select a pump that can deliver that flow at the required head after accounting for elevation, pipe friction, valves, and filtration.
4) Why does zoning change pump sizing?
When zones run sequentially, the pump only serves one zone at a time. More zones typically reduce instantaneous flow, though total daily volume stays the same.
5) How should I use the peak factor?
Apply it to cover hot spells, growth stages, or operational constraints. Values around 1.10–1.30 are common when weather swings or scheduling limits could create short-term demand spikes.
6) What buffer percentage is reasonable?
Many gardens start with 10%. Use 5% for stable, measured systems and 15% where demand data is uncertain, water quality is poor, or expansion is likely within a season.
7) When is the hydroponics circulation output useful?
It helps size circulation to meet turnover goals for mixing and oxygenation. Use it alongside pump head requirements and plumbing losses, especially when running on timed schedules.