Sprinkler Zone Planning Guide

How Sprinkler Zones Work

A sprinkler "zone" is a group of sprinkler heads that are all controlled by a single valve and run at the same time. Your system divides your yard into multiple zones because most residential water supplies don't have enough pressure and flow to run every sprinkler head simultaneously.

Think of it like circuits in your electrical panel. Just as you wouldn't run every appliance on one circuit, you can't run every sprinkler on one water line. Zones allow your system to water different areas sequentially, ensuring each zone gets adequate pressure for even coverage.

Each zone has its own electric valve (usually grouped together in a valve manifold) that is controlled by your sprinkler controller. The controller opens one valve at a time, runs that zone for the programmed duration, then moves to the next zone.

Why Zone Planning Matters

Poor zone planning leads to overwatered areas, dry spots, wasted water, and higher utility bills. Good zone planning accounts for:

• Water demand: Lawns need more water than garden beds. Mixing head types on one zone means something gets too much or too little.
• Sun exposure: South-facing areas dry out 30–50% faster than shaded north sides.
• Soil type: Sandy soils drain fast and need shorter, more frequent watering. Clay soils absorb slowly and need longer, less frequent cycles.
• Slope: Sloped areas need different run times to prevent runoff.
• Plant types: Grass, perennials, shrubs, and trees all have different water needs.

Zone Types

Calculating GPM and PSI Requirements

The two numbers that determine how many heads you can put on one zone are GPM (gallons per minute) — your available flow rate — and PSI (pounds per square inch) — your water pressure.

How to measure your GPM: Turn on an outdoor faucet fully, hold a 5-gallon bucket under it, and time how long it takes to fill. If it fills in 30 seconds, you have 10 GPM. If it takes 40 seconds, you have 7.5 GPM. Most Idaho homes on city water have 8–15 GPM available.

How to check your PSI: Attach a pressure gauge (available at hardware stores for $10) to an outdoor hose bib with all water off in the house. Static pressure should read 40–80 PSI. Most Idaho city water systems deliver 50–70 PSI.

Zone sizing rule of thumb: Add up the GPM demand of all heads on a zone. That total should be no more than 75% of your available GPM. For example, if you have 10 GPM available, each zone should use no more than 7.5 GPM. This leaves a safety margin for pressure variations and ensures adequate head performance.

Idaho Soil Types and Water Absorption

Eastern Idaho has a variety of soil types that directly impact how you should plan your zones and program your watering schedule:

• Snake River Valley (Idaho Falls, Shelley, Blackfoot): Sandy loam over volcanic rock. Drains fast — water penetrates quickly but doesn't hold moisture well. Needs more frequent, shorter watering cycles.
• Pocatello / Chubbuck area: Clay-heavy soils with good moisture retention. Absorbs slowly — run cycles may need to be split (e.g., two 10-minute runs with a 30-minute soak-in break instead of one 20-minute run) to prevent runoff.
• Rexburg / Upper Valley: Rich agricultural loam. Generally the best soil for irrigation — absorbs at a moderate rate and holds moisture well. Standard programming usually works without modification.
• Mountain areas (Driggs, Sun Valley): Rocky, well-drained soils. Similar to Idaho Falls — fast drainage requires more frequent watering.

Sun vs Shade Zone Differences

In Idaho's dry climate, sun exposure has a dramatic impact on water needs. South and west-facing areas receive intense afternoon sun and lose moisture 30–50% faster than north and east-facing areas. Your zone plan should account for this:

• Full sun zones (south/west facing): Need the most water. Program for full run times, 4–5 days per week in peak summer.
• Partial shade zones: Reduce run time by 25–30% compared to full sun zones. 3–4 days per week is usually sufficient.
• Full shade zones (north side of house): Need 40–50% less water. Over-watering shaded areas promotes fungal disease, moss, and root rot. 2–3 days per week, shorter cycles.

Slope Considerations

Many Idaho lots — particularly in subdivisions built on benchlands around Idaho Falls and Pocatello — have sloped areas. Water applied to slopes tends to run off before soaking in, wasting water and potentially causing erosion. Zone planning for slopes requires special attention:

• Keep sloped areas on separate zones from flat areas
• Use low-precipitation-rate heads (matched precipitation nozzles or rotors)
• Program cycle-and-soak scheduling: run 5–8 minutes, pause 20–30 minutes for absorption, repeat 2–3 times
• Consider drip irrigation for steep planted slopes — eliminates runoff entirely

Typical Zone Count by Lot Size

For detailed pricing breakdowns, see our Sprinkler System Cost Guide. For city-specific lot information, check our guides for Idaho Falls, Pocatello, and Rexburg.

Planning for Future Landscaping

If you're building new or planning landscape changes, consider running extra valve wire and stubbing out additional zone connections during installation. Adding a zone later means digging up your finished yard. Running the wire and pipe stub-outs during initial installation adds only $50–$100 per future zone and saves $200–$400 compared to retrofitting later.

This is especially relevant if you're coordinating sprinkler installation with a landscaping project through Idaho Yard Pros or finishing your outdoor spaces alongside a basement finishing project.