Customer asks how long each irrigation zone should run.

You can't guess run times—you need precipitation rate (PR) and soil intake rate. Here’s the field method:

1. Catch Can Test (Standard PR Measurement)

• Place 16–24 identical straight-sided cans (tuna cans work) in a grid across one zone.
• Run zone 15 min. Measure depth in each can (inches). Average them.
• PR (in/hr) = (Avg depth × 4). Example: 0.375" avg → 1.5 in/hr.

2. Calculate Base Run Time

• Target: 0.5–0.75" per cycle (clay: 0.5"; sand: 0.75").
• Run time (min) = (Target inches ÷ PR) × 60 Example: 0.5" ÷ 1.5 in/hr × 60 = 20 min.

3. Adjust for Soil & Slope (Cycle/Soak)

• If runoff occurs before target depth: split into cycles.
• Max cycle time = time until runoff starts (watch curb/gutter).
• Total run = sum of cycles. Wait 30–60 min between cycles for absorption.

4. Verify with Soil Probe

• 1 hr after irrigation, probe 6–8" deep. Soil should be moist to root zone, not soggy.

Code/Standard Refs:

• IA BMP: Catch can test per ASABE S398.1
• EPA WaterSense: Max PR 1.0 in/hr for slopes >4%
• Local ordinances often mandate cycle/soak on slopes >10% or clay soils.

Pro tip: Label each zone’s PR and run time at the controller. Re-test annually—nozzles wear, pressure changes.

To determine proper irrigation zone run times without knowing head output, follow this practical, code-aligned method based on evapotranspiration (ET) and soil moisture balance — the industry-standard approach endorsed by the Irrigation Association and aligned with water conservation codes (e.g., California’s Model Water Efficient Landscape Ordinance - MWELO, or similar local ordinances).

Step-by-Step Method:

1. Measure Precipitation Rate (in/hr) per Zone Since you don’t know head output, perform a catch can test: - Place 4–6 straight-sided cans (e.g., tuna cans) evenly spaced across the zone. - Run the zone for 15 minutes. - Measure water depth in each can (in inches), average them. - Multiply average depth by 4 to get inches per hour (precipitation rate). Example: 0.25" avg in 15 min → 1.0 in/hr.

1. Determine Weekly Water Need Use local ET data (available free from: - USDA NRCS ET Network - Your state’s cooperative extension service - Or apps like IrrigationScheduler or CropManage) Example: Cool-season grass in summer may need 1.5" per week.

1. Calculate Run Time Run Time (min/week) = (Weekly Water Need in inches) ÷ (Precipitation Rate in in/hr) × 60 Example: 1.5" needed ÷ 1.0 in/hr = 1.5 hrs → 90 minutes per week.

1. Split into Multiple Cycles To prevent runoff (especially on slopes or clay soil), divide weekly time into 2–3 shorter cycles (e.g., 3×30 min) with 30–60 min between cycles to allow infiltration.

Why This Works:

• Matches water applied to actual plant need + soil loss (ET).
• Avoids overwatering (waste, disease, runoff) and underwatering (stress).
• Complies with water efficiency codes requiring ET-based scheduling (e.g., MWELO §492.11).

Pro Tip:

If you can’t access ET data, use 1" per week as a conservative baseline for most lawns in temperate climates — adjust up/down based on soil (sandy = more, clay = less), sun exposure, and season.

Never guess run times — overwatering is the #1 cause of irrigation waste and landscape damage. If the system is old, poorly designed, or has mixed head types (rotors/sprays), consider a professional audit — many utilities offer free or low-cost irrigation evaluations.

Always check local watering restrictions — some municipalities limit days/times regardless of need. (Word count: 248)