How SprinklerMap places sprinklers automatically
How automatic sprinkler placement works in SprinklerMap: three algorithms compared on the same 97 m² garden, with measured sprinkler counts and covered area.
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How SprinklerMap works: calculation methodology
Full transparency on how the tool calculates sprinkler coverage, head loss, the number of zones and the materials list. With stated sources, formulas and limitations.
Design principles adopted
SprinklerMap applies the principles of professional irrigation design defined by ASABE (American Society of Agricultural and Biological Engineers) and the technical guidelines of Rain Bird, Hunter Industries and the Irrigation Association.
The three core principles built into the tool:
- Head-to-head coverage: the distance between adjacent sprinklers never exceeds the coverage radius. This ensures a Distribution Uniformity (DU) coefficient of 75–90%, the target value for turf areas according to IA (Irrigation Association) Best Management Practices.
- Matched Precipitation Rate (MPR): sprinklers on the same circuit must have the same flow rate per unit area. A 180° sprinkler must deliver exactly twice the flow of a 90° sprinkler of the same model, at the same radius.
- Hydrozone separation: plants with different water needs, or incompatible distribution systems (pop-up vs. drip), are never placed on the same circuit.
Sprinkler coverage calculation
Distribution model
SprinklerMap uses a simplified radial distribution model, consistent with the flow profiles published by sprinkler manufacturers. Precipitation rate (flow per unit area) is highest in the central zones and decreases toward the periphery following an approximated non-linear function.
Theoretical precipitation rate formula for sector sprinklers:
PR (mm/h) = (96.25 × Q) / (π × R² × (arc/360))
Where: Q = flow rate in L/min, R = radius in meters, arc in degrees. The constant 96.25 converts L/min/m² to mm/h. Source: Rain Bird Engineering Reference Guide, standard ASABE S436 formula.
Distribution Uniformity (DU)
The coverage simulation calculates the DU (Distribution Uniformity) of the sprinkler grid using a simplified Christiansen CU formula, based on the estimated variance of flow-per-unit-area values across the garden's different sub-areas. A DU ≥ 0.75 is considered adequate for residential use; DU ≥ 0.85 is the professional target.
Head loss calculation
Head loss along the pipes is calculated using the Hazen-Williams formula, the hydraulic industry standard for polyethylene pipe (coefficient C = 140–150 for PE):
hf = 10.67 × L × Q1.852 / (C1.852 × D4.87)
Where: L = pipe length in m, Q = flow rate in m³/s, C = Hazen-Williams coefficient, D = internal diameter in m.
Losses in solenoid valves, filters and fittings are estimated using standard K coefficients (equivalent-length method) based on the technical data of the leading manufacturers (Hunter, Rain Bird, Bermad).
Zone count calculation
The number of zones (independent hydraulic circuits) is determined by three constraints:
- Flow constraint: the sum of the sprinkler flows on a circuit never exceeds 78% of the maximum available flow (a 22% safety margin for pressure variation and mains conditions).
- Pressure constraint: the pressure available at the farthest sprinklers on the circuit must be at least equal to the minimum operating pressure of the chosen sprinkler.
- Compatibility constraint: pop-up sprinklers and drippers can never share the same circuit, due to incompatible operating pressures (2–3 bar vs. 0.5–1.5 bar).
Materials list calculation
Pipe runs are calculated by measuring the shortest path between all sprinklers in each zone (an approximated spanning-tree algorithm), plus a 10% margin for fittings, measurement error and routing changes during installation.
T-fittings are counted based on the branches along the route. Outlet fittings (saddle clamps or direct fittings) are counted one per sprinkler.
The main pipe size (25 mm, 32 mm or 40 mm) is selected based on the circuit's flow rate to keep flow velocity under 1.5 m/s (the recommended limit to reduce water hammer in PE pipe, source: Plastics Pipe Institute TR-4).
Sources for the numeric claims used on the site
| Claim | Value | Source and notes |
|---|---|---|
| Water savings with a well-designed system | 20–40% | UCANR (University of California): studies on 1,200 residential homes in Mediterranean climates, 2015–2020. Actual savings depend on pressure, exposure, soil type and prior habits. |
| Additional savings with an ET-based controller | 20–44% | EPA WaterSense program: comparative analysis of smart vs. fixed-schedule controllers on a sample of 500+ units across 12 US states, 2019. Higher values in summer, lower in spring. |
| Savings with a rain sensor | 15–30% | Florida Department of Environmental Protection: three-year study of 300 homes in a subtropical climate. Conservative figure for a Mediterranean climate with more seasonal rainfall. |
| Savings with 5–8 cm mulching | 50–70% reduction in soil evaporation | University of Georgia Cooperative Extension: evaporation studies on soils mulched with pine bark. The savings on total irrigated volume depend on the share of loss from soil evaporation (20–40%). |
| Cost of a residential system | €300–800 (50–100 m²) | Estimate based on 2024 component price lists from Hunter, Rain Bird, Gardena and Claber. Includes sprinklers, pipes, fittings, valves, controller. Excludes labor. |
| Italian mains water pressure | 2–4 bar, average 2.5–3 bar | ARERA (Italian Regulatory Authority for Energy, Networks and Environment): SII 2023 technical quality report. Guaranteed minimum service values are 1.5–2 bar; actual pressure is often higher. |
| Midday vs. morning evaporation | Up to 30% vs. under 5% | FAO Irrigation and Drainage Paper 56 (Allen et al., 1998): Penman-Monteith evapotranspiration model. Direct evaporation losses during overhead irrigation depend on temperature, radiation and wind. |
The figures shown on the site are indicative and represent typical scenarios under normal conditions. Actual savings depend on specific local factors.
Stated limitations of the tool
- SprinklerMap does not account for steeply sloped terrain (>15%), which requires elevation-differentiated pressure calculations.
- The water distribution model is simplified: it does not simulate the effect of wind on sprinkler throw.
- Prices in the materials list are indicative and based on 2024 price lists. Actual prices vary by retailer and country.
- The tool is designed for residential systems (gardens up to about 2,000 m²). For larger or agricultural systems, a certified irrigation designer or agronomist engineer is recommended.
Questions about the methodology? Contact us. To use the tool: open SprinklerMap →
Deep dives on the algorithms
Two pages on how the app's automation works, with the same worked examples on the same garden:
The two water simulations: how much water arrives, and how fast
How SprinklerMap's two water simulations work: Water Coverage measures the amount of water against plant need, Runoff Risk measures the rate against soil absorption. With measurements from the same garden.
Read →