Sprinkler System Guide

Zone planning, head types and spacing, pipe sizing, controller programming, and winterization

Understanding Irrigation System Basics

A sprinkler irrigation system delivers water through a network of pipes, valves, and spray heads controlled by an automatic timer. Properly designed systems save water (vs hand watering), improve lawn health, increase property value, and save time.

The key to an effective system is matching water delivery rate (precipitation rate in inches/hour) to plant water needs and soil infiltration rate. Poor design causes runoff, dry spots, over-watering, and high water bills.

Key Principle: Irrigation systems must be designed around your home's available water pressure and flow rate (GPM). Exceeding available flow causes weak pressure, inconsistent coverage, and valve malfunction. Always calculate GPM and pressure before designing zones.

Zone Planning by Plant Type and Sun Exposure

Zones are separate circuits controlled by individual valves, allowing different areas to water on different schedules. Proper zoning matches water delivery to plant needs and environmental conditions.

Fundamental Zoning Rules

✓ Never mix head types in one zone: Rotary heads (0.4-0.6 in/hr) and spray heads (1.5-2.0 in/hr) have vastly different precipitation rates. Mixing causes over/under watering.
✓ Separate by sun exposure: Full sun areas need more water than shaded areas. Different zones for each.
✓ Separate by plant type: Turf (lawn) vs shrubs/gardens vs trees—different water needs and head types
✓ Separate slopes from flat areas: Slopes require slower application rate to prevent runoff
✓ Separate soil types: Sand drains fast (more frequent, shorter cycles). Clay drains slowly (less frequent, longer cycles or multiple short cycles).
✓ GPM per zone limit: Don't exceed 75-80% of available GPM per zone to maintain pressure

Zone Type	Head Type	Runtime	Frequency	Notes
Front Lawn (Full Sun)	Rotary/Rotor heads	45-60 min	2-3x per week	Highest water need. Deep watering encourages root growth. Early morning best.
Back Lawn (Partial Shade)	Rotary heads	30-45 min	2x per week	Less evaporation. Separate zone from full sun—needs 20-30% less water.
Shrub Beds	Drip line or spray heads on risers	20-30 min	1-2x per week	Mulch retains moisture—less frequent watering. Drip delivers to roots, not foliage.
Flower/Vegetable Gardens	Drip line or micro-spray	30-45 min	Daily to 2x/week	High water need. Drip preferred for efficiency. Adjust by plant type.
Slopes	Matched precipitation rotary heads or drip	Multiple 10-15 min cycles	2-3x per week	Cycle & soak: run 15 min, pause 30 min, repeat 2-3x to prevent runoff.
Trees (Established)	Drip line or bubblers	60-90 min	1x per week or biweekly	Deep, infrequent watering. Position emitters at drip line (edge of canopy).
Parking Strips (between sidewalk & street)	Strip spray nozzles or rotary	15-20 min	2-3x per week	Hot, harsh conditions. Separate zone—may need more frequent watering than main lawn.

Calculating Required Number of Zones

Step 1: Determine Available GPM

Measure flow rate at exterior hose bib with bucket and timer. Typical: 8-12 GPM residential.

Step 2: Calculate Usable GPM per Zone

Use 75-80% of total (maintain pressure). Example: 10 GPM total × 0.75 = 7.5 GPM per zone max.

Step 3: Determine Head Count per Zone

Rotary heads use 2-6 GPM each. Spray heads use 0.5-2 GPM each. Example: 7.5 GPM ÷ 3 GPM per head = 2-3 rotary heads per zone.

Step 4: Divide Property into Zones

Typical 5,000 sq ft property: 4-6 zones (front lawn, back lawn, side yard, shrubs, garden, parkway).

Sprinkler Head Types and Spacing

Head Type	Radius	GPM	Precip Rate	Spacing	Best Use
Rotary / Rotor Heads	15-50 ft	2-6 GPM	0.4-0.6 in/hr	25-35 ft apart	Large lawn areas. Most efficient for turf over 500 sq ft. Slower precipitation prevents runoff. Pop-up or shrub mount.
Fixed Spray Heads	4-15 ft	0.5-2 GPM	1.5-2.0 in/hr	8-15 ft apart	Small to medium lawns, narrow areas, shrub beds. Fast precipitation—shorter run times. Many nozzle patterns (full, half, quarter circle, strip).
Rotary Nozzles (on spray bodies)	15-30 ft	0.5-1.5 GPM	0.4-0.6 in/hr	15-20 ft apart	Retrofit for spray head zones—lower precipitation, better efficiency. Good for slopes and clay soil. Matched precipitation.
Drip Emitters (inline)	N/A (point source)	0.5-2 GPH per emitter	Highly variable	12-24" apart on tubing	Shrubs, trees, gardens, flower beds. Most water-efficient (90-95%). Delivers water directly to root zone. Low pressure (15-30 PSI).
Drip Line (porous tubing)	N/A (line source)	Varies by length	N/A	Continuous coverage	Vegetable gardens, dense plantings, raised beds. Soaker hose alternative. Consistent moisture along entire length.
Bubblers	1-3 ft	0.5-2 GPM	Very high	One per plant/tree	Trees, large shrubs. Floods root zone quickly. Use in basin around plant. Good for deep-rooted plants.
Micro-Spray / Misters	2-10 ft	0.25-1 GPM	High	4-8 ft apart	Flower beds, ground cover, small shrubs. Gentle spray. Can be on stake or riser. Low pressure compatible with drip zones.
Impact Sprinklers	20-80 ft	4-15 GPM	0.3-0.5 in/hr	35-50 ft apart	Large areas, agricultural, sports fields. Distinctive "chk-chk" sound. Durable. Not typical residential but useful for very large properties.

Head-to-Head Coverage Rule

• Principle: Space heads so spray from one head reaches the next head (100% overlap at edge). This ensures uniform coverage with no dry spots.
• Formula: Head spacing = 50-60% of diameter (or 100-120% of radius)
• Example: Rotary head with 30 ft radius → space heads 30-36 ft apart
• Why not further: Wind drift, pressure variation, and uneven terrain reduce effective radius. Overlap compensates.
• Triangular pattern: Most efficient layout—heads at corners of equilateral triangles. Better than square grid.

Precipitation Rate and Watering Time

Precipitation Rate Formula:

Precip Rate (in/hr) = (96.3 × GPM per head) ÷ (Spacing × Spacing)

Example Calculation:

• Rotary heads: 4 GPM each, spaced 30 ft × 30 ft
• Precip rate = (96.3 × 4) ÷ (30 × 30) = 0.43 in/hr
• To apply 1 inch of water: 1 ÷ 0.43 = 2.3 hours runtime

Typical precipitation rates:

• Rotary heads: 0.4-0.6 in/hr (slow—good for most soils)
• Spray heads: 1.5-2.0 in/hr (fast—can cause runoff on clay or slopes)
• Drip: 0.1-0.3 in/hr equivalent (very slow, highly efficient)

Matched Precipitation Nozzles

Modern spray and rotary nozzles are available as matched precipitation (MP) sets, where all nozzle patterns (full circle, half circle, quarter circle) deliver the same precipitation rate. This is critical for uniform watering.

Traditional nozzles: Quarter-circle puts down 4x more water than full-circle at same runtime (causes over-watering in corners)
MP nozzles: Quarter-circle uses 1/4 the GPM of full-circle, same precip rate (even watering)
Recommendation: Always use matched precipitation nozzles. Worth the extra cost for uniform coverage.

Pipe Sizing by GPM and Friction Loss

Proper pipe sizing is critical to maintain pressure and flow throughout the system. Friction loss occurs as water flows through pipes—smaller pipes and longer runs = more friction loss = pressure drop.

Pipe Size	Maximum GPM	Friction Loss	Typical Use
3/4" PVC (SCH 40)	8-10 GPM max	~7 PSI per 100 ft @ 8 GPM	Lateral lines (from valve to heads). Most common for zone piping. Do not use for mainline if multiple zones.
1" PVC (SCH 40)	12-16 GPM max	~4 PSI per 100 ft @ 12 GPM	Mainline or laterals for high-flow zones (large rotary heads). Common mainline size for residential.
1-1/4" PVC (SCH 40)	20-25 GPM max	~2.5 PSI per 100 ft @ 20 GPM	Mainline for systems with multiple high-flow zones or long runs. Professional installations.
1-1/2" PVC (SCH 40)	30+ GPM	~1.5 PSI per 100 ft @ 25 GPM	Mainline for large commercial systems or very long residential runs (200+ ft from source).
1/2" PVC or Poly	4-6 GPM max	~15 PSI per 100 ft @ 5 GPM	Short runs to individual spray heads or drip zones. High friction loss—avoid long runs. Not recommended for mainline.
Poly Tubing (1/2" to 3/4")	Varies (lower than PVC)	Higher than PVC (rougher interior)	Drip zones, temporary systems, easy retrofit. Flexible but less efficient flow. Use compression fittings.

Pipe Sizing Guidelines

• Mainline (POC to valves): Size for total system flow OR largest single zone + 20-30%. Use 1" minimum for most residential. 1-1/4" if distance over 100 ft or high flow.
• Lateral lines (valve to heads): 3/4" sufficient for most zones (up to 8-10 GPM). Increase to 1" for high-flow zones (large rotary heads, 10+ GPM).
• Velocity rule: Keep water velocity under 5 feet/second to minimize friction loss and water hammer. Higher velocity = more friction.
• Pressure loss budget: Target less than 10-15% pressure loss from POC to furthest head. Example: 60 PSI source, allow max 6-9 PSI loss.
• When to upsize: If calculated friction loss exceeds 15-20% of available pressure, upsize to next larger pipe diameter

PVC Pipe Types

Schedule 40 (white or gray): Standard for irrigation. Thicker wall, handles full pressure. UV-resistant if gray. Use for all exposed or high-pressure runs.
Class 200 (thinner wall): Lighter and cheaper. Suitable for low-pressure (under 200 PSI) residential irrigation buried at proper depth. More prone to damage.
Schedule 80 (dark gray): Heaviest wall, highest pressure rating. Overkill for typical residential. Use in high-traffic areas or above-ground exposed runs.
Bury depth: Minimum 6-8" for freeze protection in cold climates, 6" minimum in warm climates (protects from damage)

Valve Installation and Manifold Setup

Valve Box Location and Setup

• Centralized manifold: Group all zone valves together in one or two valve boxes near water source. Easier maintenance and wire runs.
• Distributed valves: Place valve boxes near zones they control. Reduces pipe runs but more valve boxes to maintain.
• Valve box size: 10×15" for 2-3 valves, 12×17" for 4-6 valves. Allow room to work on valves.
• Location: Accessible, not under permanent structures, level with ground, away from trees (root intrusion)
• Depth: Top of valve should be 4-6" below grade. Allows valve box lid to sit flush with ground.

Valve Selection and Components

• Anti-siphon valves: Have built-in backflow prevention. Install 6-12" above highest head. Simple but must be above grade (visible).
• In-line valves: No backflow device. Install underground in valve box. Requires separate backflow preventer at POC. Cleaner look.
• Valve size: Match pipe size. 3/4" or 1" most common residential. Larger valves for higher GPM.
• Flow control: Many valves have adjustable flow control knob—allows fine-tuning zone pressure without adjusting at controller
• Manual bleed: Small screw allows manual operation without controller (for testing)
• Solenoid: 24V AC solenoid activates valve. Wired to controller. Can replace if solenoid fails without replacing entire valve.

Manifold Plumbing Best Practices

• Mainline to manifold: Run single pipe from POC/backflow preventer to valve manifold. Tee off for each zone valve.
• Unions: Install union before each valve for easy removal/replacement
• Valve orientation: Flow arrow on valve body points away from mainline, toward zone
• Drains: Install automatic drain valves at low points to prevent freeze damage (cold climates)
• Flush ports: Install flush valve (simple ball valve) after last zone valve to flush mainline during installation
• Wire waterproofing: Use waterproof wire connectors. Standard wire nuts will corrode. Direct-bury wire rated for underground.

Backflow Prevention (Critical for Safety)

Backflow preventers protect drinking water from contamination if irrigation water siphons back into house supply. Required by code in most areas.

Pressure Vacuum Breaker (PVB): Most common residential. Install on mainline before any valves, 12" above highest head. Must be outdoor. $50-150.
Reduced Pressure Zone (RPZ): Higher protection. Required for commercial, high-hazard, or if fertilizer injector used. Requires annual testing. Install above grade. $200-500.
Atmospheric Vacuum Breaker (AVB): Individual valves with built-in backflow. Simple but must be 6"+ above heads. Common on hose-bib systems.
Installation: Professional plumber recommended for connection to house water supply and backflow device installation (may require permit and inspection)

Controller Programming Basics

Controller Types

• Basic timer: Simple scheduling (days, start times, runtimes). Runs regardless of weather. $30-80. Good for small, simple systems.
• Weather-based (ET) controller: Adjusts watering based on local weather data (evapotranspiration). More efficient. $100-300. Best for water conservation.
• Smart/WiFi controller: Connects to internet, uses hyperlocal weather, remote control via app, reporting. $150-400. Ultimate convenience and efficiency.
• Number of stations: Choose controller with enough stations (zones) + 2-3 extra for expansion. 6-station common for small yards, 12-station for larger properties.

Programming Steps (Basic Controller)

Step 1: Set Current Date/Time

• Required for schedule to run correctly
• Some controllers lose settings if power interrupted—may need battery backup

Step 2: Set Watering Days

• Specific days: Mon/Wed/Fri or Tue/Thu/Sat typical for established lawns
• Interval: Every 3 days or every other day
• Odd/Even days: For water restrictions (odd address = odd days)
• Recommendation: 2-3 days per week for most lawns. Daily only for new seed or extreme heat.

Step 3: Set Start Times

• Best time: 4-6am (before sunrise). Minimal wind, low evaporation, time to dry before evening (prevents disease).
• Multiple start times: Can program 2-3 start times per day. Use for cycle & soak on slopes or to split long runtimes.
• Avoid: Midday (high evaporation loss, 30-50% waste). Evening (stays wet all night, encourages fungus).

Step 4: Set Zone Runtimes

• Based on precipitation rate, soil type, plant type, sun exposure
• Example: Full-sun lawn with rotary heads: 45-60 min, 2-3x per week
• Shrubs with drip: 30-45 min, 1-2x per week
• Start conservative—easier to increase than decrease. Observe and adjust.

Step 5: Set Seasonal Adjust

• Master valve that scales all zone runtimes by percentage (50%-150% typical)
• Set to 100% in peak summer. Reduce to 70-80% in spring/fall, 30-50% in winter.
• Easier than reprogramming each zone seasonally

Watering Duration Guidelines

• Goal: Apply 1-1.5 inches per week total for cool-season grass (more in hot climates, less in cool climates)
• Formula: Runtime = (Target inches per week ÷ Days per week) ÷ Precip rate
• Example: 1.5" per week, water 3x/week, precip rate 0.5 in/hr: (1.5 ÷ 3) ÷ 0.5 = 1 hour per session
• Sandy soil: More frequent, shorter duration (every other day, 20-30 min)
• Clay soil: Less frequent, longer duration or cycle & soak (2x/week, 45-60 min or 3× 20min cycles)
• Slopes: Cycle & soak: Run 15 min, pause 30-60 min (soak-in time), repeat 2-3x

Smart Controller Features

Rain skip: Skips watering if recent rain or rain in forecast (adjustable threshold)
Soil moisture integration: Uses in-ground sensors to water only when needed (most efficient)
ET adjustment: Automatically adjusts based on temperature, humidity, solar radiation, wind
Flow monitoring: Detects leaks or broken pipes by monitoring flow rate
Remote access: Control from smartphone—check status, adjust schedules, manual run
Water usage reports: Track consumption, identify savings opportunities
ROI: Smart controllers typically save 20-50% on water bills. Payback in 1-3 years.

Winterization Blowout Procedures (Cold Climates)

In climates where temperatures drop below freezing, irrigation systems must be winterized to prevent freeze damage. Water left in pipes expands when frozen, cracking pipes, valves, and heads—expensive repairs.

When to Winterize

• Timing: Before first hard freeze (when temperatures drop below 25-28°F). Typically late October to early November in most northern climates.
• Too early: Lawn may need water in warm fall weeks
• Too late: Risk freeze damage if unexpected cold snap
• Monitor forecast: Watch for first freeze warning and winterize within 1-2 weeks before
• Not needed: Climates that never freeze (South Florida, Southern California, etc.) don't require winterization

Winterization Methods

• Compressed air blowout (best method): Force all water out with compressed air. Most thorough. Requires compressor or professional service.
• Manual drain method: Open manual drain valves and let gravity drain water. Only works if system designed with drain valves at low points. Not thorough—water remains in heads.
• Automatic drain valves: Spring-loaded valves open when pressure drops, drain pipes automatically. Should still blow out for full protection.
• Most effective: Compressed air blowout, even if system has drain valves. Only method that clears water from sprinkler heads.

Compressed Air Blowout Procedure

Equipment Needed:

• Air compressor: 10+ CFM (cubic feet per minute). 20+ CFM preferred. Larger systems need more CFM.
• PSI: 50-80 PSI max. Never exceed 80 PSI—can damage components.
• Compressor size: Portable compressor 5-10 HP typical. Can rent for $40-80/day.
• Quick-connect fitting or blow-out adapter for connecting to system

Step-by-Step Process:

Step 1: Shut Off Water Supply

• Turn off main water supply to irrigation system
• Close ball valve or shut-off valve at POC
• Do NOT turn off backflow preventer valves—leave open to prevent damage

Step 2: Connect Compressor

• Locate blow-out port or hose bib connection near backflow preventer or mainline
• Attach compressor hose with quick-connect or threaded adapter
• Ensure good seal—leaks reduce effectiveness

Step 3: Set Compressor Pressure

• Set regulator to 50 PSI for standard spray heads
• 40 PSI for rotors (lower pressure to avoid damage)
• NEVER exceed 80 PSI—can blow apart pipes and fittings

Step 4: Blow Out One Zone at a Time

• Use controller to activate first zone (or manually open valve)
• Start compressor—air flows through zone, forcing water out
• Watch heads—when only mist comes out (no water), zone is clear (typically 2-3 minutes)
• Turn off zone before heads stop misting completely (prevents overheating compressor)
• Wait 30-60 seconds between zones (let compressor tank refill)
• Repeat for each zone

Step 5: Blow Out Mainline

• After all zones cleared, disconnect compressor from blow-out port
• Open all valve manual bleeds to clear manifold
• Some systems have mainline drain—open to drain remaining water

Step 6: Drain Backflow Preventer

• Open test cocks and drain valves on backflow device
• Leave open all winter (allows any residual water to drain and prevents freeze damage)
• Some backflow devices have removable internal parts for winter—consult manual

Step 7: Shut Down Controller

• Turn controller to "OFF" or "Rain" mode to prevent accidental activation
• Remove battery backup if equipped (prevents drain)
• Some prefer unplugging controller for season

Professional Winterization

Cost: $50-150 depending on system size and region (typical: $75-100)
Advantages: Proper equipment, experience, insurance coverage if damage occurs, convenience
DIY feasibility: Possible with rented compressor but requires some technical knowledge
Repair costs: Freeze damage can cost $500-2,000+ to repair (burst pipes, broken heads, cracked valves). Winterization is cheap insurance.
Spring start-up: Most pros charge $50-100 to reactivate system, check for winter damage, adjust heads

Additional Winter Protection

• Insulate backflow preventer: Wrap with insulation tape or foam covers (available at hardware stores). Critical if above-ground in harsh climates.
• Cover valve boxes: Pack insulation (straw, foam) in valve boxes for extra protection
• Drain hose bib: If separate hose bib used for irrigation connection, drain and cap it
• Store controller: If outdoor controller exposed to harsh weather, remove battery and protect from moisture

Tools and Materials for Installation

Tools

Trenching shovel or edger
PVC cutter or hack saw
PVC primer and cement
Tape measure and marking paint
String line and stakes
Adjustable wrench
Screwdrivers
Wire strippers
Teflon tape
Level

Materials

PVC pipe (3/4", 1", as calculated)
PVC fittings (elbows, tees, couplings)
Zone valves (qty = number of zones)
Sprinkler heads (rotary, spray, as designed)
Controller (stations = zones + buffer)
Backflow preventer
Valve boxes
Direct-bury wire (18-gauge, multi-strand)
Waterproof wire connectors
Gravel or sand (for pipe bedding)

Safety and Code Considerations

Call Before You Dig (811): Always call 811 at least 2-3 business days before digging to have underground utilities marked (gas, electric, water, sewer, cable, phone). Hitting a gas or electric line can cause explosion, electrocution, or death. Service is free. Fines for not calling can be $10,000+. You are responsible for damage to utilities if you don't call.

Backflow Prevention Required: Cross-connection from irrigation to potable water is a serious health hazard. Backflow preventers are required by plumbing code in nearly all jurisdictions. Installation must comply with local code—often requires licensed plumber and inspection. Using system without proper backflow prevention can contaminate your and neighbors' drinking water and result in fines or mandatory removal.

Electrical Safety: Controllers run on 110V AC power—can cause electrocution if improperly wired. Install with GFCI protection. Hire licensed electrician for outdoor outlet installation if needed. Never work on controller with wet hands. Turn off power before opening controller or working on wiring. Low-voltage (24V) wiring to valves is safer but still requires waterproof connections.

Winterization Pressure: Never exceed 80 PSI during blow-out. Excessive pressure can burst pipes, blow apart fittings, damage sprinkler heads (causing them to become projectiles), and cause serious injury. Always wear safety glasses during blow-out. Stand away from heads when activating zone. Compressed air is dangerous—can cause injection injuries.

Water Conservation and Regulations: Many areas have watering restrictions (specific days, times, duration limits) especially during drought. Violating restrictions can result in fines ($100-500+ per violation). Smart controllers help maintain compliance. Over-watering wastes a precious resource—design system for efficiency, not excess. Install rain sensors or smart controllers with weather integration.

Note: Irrigation system installation often requires permits, especially for connection to potable water supply and backflow preventer installation. Requirements vary widely by jurisdiction. Improper installation can cause property damage (flooding, erosion), health hazards (backflow contamination), and void homeowner's insurance. When uncertain, hire licensed irrigation contractor. DIY installation is feasible for homeowners with plumbing experience, but professional design consultation recommended for complex properties or to maximize efficiency.

Quick Reference Summary

Key Design Rules

Never mix rotary and spray heads in same zone
Head-to-head coverage (space at 50-60% of diameter)
Separate zones by plant type and sun exposure
Use 75% of available GPM per zone max
Water early morning (4-6am) for best results

Key Takeaways

Backflow prevention is required—not optional
Call 811 before digging—every time, no exceptions
Winterize before first freeze in cold climates
Smart controllers save 20-50% water (good ROI)
Professional design/installation recommended for complex systems

Disclaimer: This guide provides general information about residential irrigation systems. Local codes, water pressure, soil types, climate conditions, and plant water requirements vary dramatically. Irrigation system design is complex—poor design wastes water and money while potentially damaging your landscape. Backflow prevention requirements are strictly regulated for public health protection—non-compliance can result in fines and mandatory system removal. Always verify local building codes, obtain required permits, call 811 before digging, and consider professional design consultation or installation for optimal results. Improper winterization causes expensive freeze damage. When in doubt, hire a licensed irrigation contractor.