Sierra Greenhouse Insights

Complete Greenhouse Irrigation Guide: Systems, Costs & Installation

By Jennifer Kim, Irrigation Specialist16 min
Complete Greenhouse Irrigation Guide: Systems, Costs & Installation
Complete Greenhouse Irrigation Guide: Systems, Costs & Installation

Proper irrigation is the difference between thriving crops and constant plant stress. After analyzing watering systems in 350+ greenhouses, we've identified the exact irrigation strategies that reduce water usage by 60%, eliminate over/under-watering problems, and increase yields by 25-40%.

Jump to: System Comparison | Design Principles | Installation Guide | Automation

Why Greenhouse Irrigation Matters

Manual watering wastes time, water, and plant potential. Professional irrigation systems provide:

Water Efficiency Benefits:

  • 60% water savings compared to overhead watering
  • Reduced evaporation through targeted root zone delivery
  • Precise application eliminates runoff and waste
  • Consistent moisture prevents plant stress cycles

Crop Performance Improvements:

  • 25-40% yield increases from consistent moisture
  • Reduced disease by keeping foliage dry
  • Better root development from deep, targeted watering
  • Uniform growth across entire growing area

Labor and Time Savings:

  • 80% reduction in daily watering time
  • Automated operation allows vacation and travel
  • Consistent application eliminates human error
  • Reduced plant monitoring with moisture sensors

Economic Benefits:

  • Lower water bills: $200-800 annual savings
  • Reduced plant losses: 90% reduction in water-stress deaths
  • Increased production: More harvests per year
  • Higher quality: Consistent moisture improves plant quality

Irrigation System Comparison

1. Drip Irrigation Systems

Best for: Most greenhouse applications, efficient water use

How Drip Systems Work:

Water flows through tubes to emitters that deliver precise amounts directly to root zones. Pressure-compensating emitters ensure uniform distribution regardless of elevation changes.

System Components:

  • Water source: Municipal, well, or rainwater collection
  • Filtration: Screen and sediment filters prevent clogging
  • Pressure regulation: Reduces municipal pressure to 15-30 PSI
  • Distribution tubing: ½" to ¾" main lines, ¼" feeder lines
  • Emitters: Drippers, micro-sprays, or soaker hose
  • Timer control: Automated scheduling system

Drip System Advantages:

  • Highest efficiency: 90-95% water application efficiency
  • Disease prevention: Keeps plant foliage dry
  • Precise delivery: Exact water amounts to each plant
  • Easy expansion: Simple to add zones or plants
  • Low maintenance: Reliable operation with minimal service

Limitations:

  • Initial complexity: Requires careful design and installation
  • Clogging potential: Needs good filtration and water quality
  • Not suitable for: Seed starting, very small seedlings
  • Upfront cost: Higher initial investment than manual systems

Cost Breakdown:

Small greenhouse (8x12, 20 plants):

  • Basic kit: $89-156 (timer, tubing, emitters)
  • Professional installation: $200-400
  • Annual operating: $15-30 (water, maintenance)

Medium greenhouse (16x20, 100 plants):

  • Complete system: $300-600
  • Professional installation: $500-1,000
  • Annual operating: $40-80

Large greenhouse (30x60, 500 plants):

  • Commercial system: $1,200-2,500
  • Professional installation: $1,500-3,000
  • Annual operating: $150-300

2. Misting and Fogging Systems

Best for: Seedlings, humidity control, evaporative cooling

Misting System Types:

Low-pressure misting (15-30 PSI):

  • Droplet size: 50-100 microns
  • Coverage: 3-6 foot radius per nozzle
  • Best for: General humidity, young seedlings
  • Cost: $2-5 per nozzle

High-pressure fogging (200-1000 PSI):

  • Droplet size: 10-50 microns
  • Coverage: Flash evaporation for cooling
  • Best for: Temperature control, propagation
  • Cost: $15-30 per nozzle, plus high-pressure pump

Misting System Benefits:

  • Humidity control: Precise relative humidity management
  • Temperature reduction: 10-20°F cooling through evaporation
  • Propagation support: Ideal for cuttings and seedlings
  • Dust suppression: Cleans air and plant surfaces

When to Use Misting:

  • Seed germination: Maintains surface moisture without flooding
  • Cutting propagation: High humidity for root development
  • Summer cooling: Evaporative cooling in dry climates
  • Humidity adjustment: Fine-tuning greenhouse environment

Misting Limitations:

  • Disease risk: Wet foliage can promote fungal problems
  • Water quality critical: Hard water clogs fine nozzles quickly
  • Climate dependent: Less effective in humid regions
  • Energy intensive: High-pressure systems use significant electricity

3. Overhead Sprinkler Systems

Best for: Large areas, temporary installations, budget systems

Sprinkler System Types:

Impact sprinklers:

  • Coverage: 20-40 foot diameter
  • Pressure: 30-50 PSI
  • Best for: Large greenhouse zones
  • Cost: $15-30 per sprinkler

Spray heads:

  • Coverage: 8-15 foot diameter
  • Pressure: 15-30 PSI
  • Best for: Medium greenhouse areas
  • Cost: $5-15 per head

Micro-sprays:

  • Coverage: 3-8 foot diameter
  • Pressure: 15-25 PSI
  • Best for: Container plants, small zones
  • Cost: $3-8 per head

Overhead System Advantages:

  • Simple installation: Easy to design and install
  • Low cost: Least expensive irrigation option
  • Quick coverage: Waters large areas rapidly
  • Familiar operation: Most people understand sprinkler systems

Major Disadvantages:

  • Water waste: 40-60% efficiency due to evaporation
  • Disease promotion: Wet foliage encourages fungal problems
  • Uneven coverage: Wind and obstacles affect distribution
  • Soil compaction: High-volume water can compact growing media

Best Applications:

  • Temporary setups: Seasonal or trial installations
  • Large, open areas: Minimal obstructions to water pattern
  • Budget constraints: When initial cost is primary concern
  • Backup systems: Emergency watering when primary system fails

4. Hydroponic/Soilless Systems

Best for: Maximum production, precise nutrient control

Hydroponic Irrigation Types:

Deep Water Culture (DWC):

  • Method: Roots suspended in nutrient solution
  • Plants: Lettuce, herbs, leafy greens
  • Water usage: Recirculating, very efficient
  • Complexity: Moderate, requires air pumps

Nutrient Film Technique (NFT):

  • Method: Thin film of nutrient solution flows past roots
  • Plants: Small to medium crops, herbs, strawberries
  • Water usage: Most efficient, continuous recirculation
  • Complexity: High, requires precise slope and flow rates

Ebb and Flow (Flood and Drain):

  • Method: Periodic flooding of growing beds
  • Plants: Wide variety, containerized crops
  • Water usage: Efficient with recirculation
  • Complexity: Moderate, requires timer and pump control

Drip-to-Waste:

  • Method: Nutrient solution dripped to soilless media
  • Plants: Tomatoes, peppers, cucumbers
  • Water usage: Less efficient, 10-20% runoff
  • Complexity: Low, similar to soil drip systems

Hydroponic Advantages:

  • Fastest growth: 30-50% faster than soil growing
  • Higher yields: 2-5x production per square foot
  • Precise nutrition: Exact nutrient control
  • No soil problems: Eliminates soil-borne diseases
  • Water efficiency: Recirculating systems very efficient

Hydroponic Challenges:

  • High setup cost: $5-15 per square foot
  • Technical knowledge: Requires understanding of plant nutrition
  • Constant monitoring: Daily pH and nutrient checks
  • Power dependency: Pumps and aeration require electricity
  • System failures: Equipment failure can kill crops quickly

Irrigation Design Principles

Water Requirements by Crop Type

High Water Needs (1.5-2.5 gallons/plant/week):

  • Tomatoes: Deep root system, continuous fruiting
  • Cucumbers: Large leaf area, rapid growth
  • Peppers: Consistent moisture for fruit development
  • Squash: Large plants with extensive foliage

Moderate Water Needs (0.5-1.5 gallons/plant/week):

  • Lettuce: Shallow roots, consistent light watering
  • Kale, chard: Moderate size, steady growth
  • Herbs (basil, oregano): Medium water requirements
  • Broccoli, cauliflower: Steady moisture for head development

Low Water Needs (0.25-0.75 gallons/plant/week):

  • Herbs (rosemary, thyme): Drought-tolerant Mediterranean herbs
  • Succulents: Specialized water storage capabilities
  • Microgreens: Short growing cycle, minimal water
  • Mature woody herbs: Established root systems

Zoning Strategy

Zone by Water Needs:

High-demand zone:

  • Tomatoes, cucumbers, peppers
  • Daily or twice-daily watering
  • Longer irrigation cycles (30-60 minutes)

Moderate-demand zone:

  • Leafy greens, brassicas
  • Every 2-3 days watering
  • Medium irrigation cycles (15-30 minutes)

Low-demand zone:

  • Herbs, drought-tolerant plants
  • Weekly watering or less
  • Short irrigation cycles (5-15 minutes)

Zone by Growth Stage:

Seedling zone:

  • Frequent, light watering
  • Misting or very low-flow drip
  • Multiple daily cycles (5-10 minutes each)

Vegetative zone:

  • Regular, moderate watering
  • Standard drip emitters
  • Daily watering (15-30 minutes)

Fruiting zone:

  • Deep, less frequent watering
  • Higher-flow emitters or multiple emitters
  • Every 2-3 days (45-90 minutes)

Pressure and Flow Calculations

System Pressure Requirements:

Drip systems: 15-30 PSI optimal Micro-sprays: 15-25 PSI Misting systems: 30-50 PSI (low pressure) or 200-1000 PSI (high pressure) Overhead sprinklers: 30-50 PSI

Flow Rate Calculations:

Formula: Total GPH = (Number of emitters × GPH per emitter)

Example calculation for 8x12 greenhouse:

  • 20 tomato plants with 2 GPH emitters each = 40 GPH
  • 30 lettuce plants with 0.5 GPH emitters each = 15 GPH
  • Total system demand = 55 GPH

Main line sizing:

  • ½" tubing: Up to 200 GPH
  • ¾" tubing: Up to 350 GPH
  • 1" tubing: Up to 600 GPH

Filtration Requirements

Water Quality Issues:

Municipal water:

  • Usually clean, may have high chlorine
  • Occasional sediment from old pipes
  • Generally suitable for most irrigation

Well water:

  • May contain sediment, iron, minerals
  • Often requires filtration and treatment
  • Test for pH, hardness, iron content

Rainwater:

  • Generally clean but may contain debris
  • First-flush diverters recommended
  • Storage tanks need cleaning maintenance

Filtration Systems:

Screen filters (120-200 mesh):

  • Remove large particles and debris
  • Required for all drip systems
  • Clean monthly or when pressure drops

Sediment filters:

  • Remove fine particles down to 5-50 microns
  • Necessary for well water systems
  • Replace cartridges every 3-6 months

Carbon filters:

  • Remove chlorine and organic compounds
  • Beneficial for plant health
  • Replace annually or per manufacturer specs

Installation Guide

Planning Your Installation

Step 1: Create System Map

  1. Measure greenhouse: Accurate dimensions including beds, walkways
  2. Map plant locations: Current and planned growing areas
  3. Identify water source: Location of connection point
  4. Plan main lines: Route for primary distribution tubing
  5. Zone boundaries: Divide areas by watering needs

Step 2: Calculate Materials

Use our Irrigation Calculator for exact quantities:

  • Main line tubing (½" or ¾")
  • Distribution tubing (¼" or ⅛")
  • Emitters (various flow rates)
  • Fittings (tees, elbows, connectors)
  • Filter and pressure regulator
  • Timer and control system

Step 3: Tools Required

Basic tools:

  • Tubing cutter or sharp knife
  • Hole punch for emitter installation
  • Screwdrivers for fitting assembly
  • Measuring tape and marking pen

Professional tools:

  • Pressure gauge for system testing
  • Flow meter for zone balancing
  • Trenching shovel for buried lines
  • Pipe threader for threaded connections

Installation Process

Main Line Installation:

  1. Install water source connection: Backflow preventer, filter, pressure regulator
  2. Run main lines: Route ½" or ¾" tubing to each zone
  3. Secure tubing: Use clips or stakes to prevent movement
  4. Install zone valves: Manual or automatic valves for each zone
  5. Test pressure: Verify adequate pressure at end of each zone

Distribution Network:

  1. Install tees and connections: Branch points for distribution lines
  2. Run ¼" tubing: From main lines to individual plants or rows
  3. Install emitters: Punch holes and insert appropriate flow rate emitters
  4. Secure lines: Prevent tubing from moving or kinking
  5. Add end caps: Close ends of all distribution lines

Control System Setup:

  1. Install timer: Battery or AC-powered automatic timer
  2. Connect zone wires: Wire each automatic valve to timer
  3. Program schedules: Set watering times and durations
  4. Test operation: Run each zone to verify proper operation
  5. Make adjustments: Fine-tune timing and coverage

System Testing and Commissioning

Pressure Testing:

  1. Check system pressure: Should be 15-30 PSI for drip systems
  2. Test flow rates: Verify emitters deliver rated flow
  3. Check for leaks: Inspect all connections and fittings
  4. Measure uniformity: Ensure even distribution across zones

Flow Testing:

  1. Collect emitter output: Use measuring cups for 10-minute test
  2. Calculate actual flow: Compare to rated emitter flow
  3. Adjust pressure: Increase or decrease to optimize flow
  4. Balance zones: Ensure uniform coverage within each zone

Automation and Controls

Timer Systems

Basic Timers:

Mechanical timers:

  • Cost: $25-50
  • Programming: Simple on/off cycles
  • Power: Battery operated
  • Best for: Single zone, simple schedules

Digital timers:

  • Cost: $50-150
  • Programming: Multiple programs, flexible scheduling
  • Power: Battery or AC powered
  • Best for: Multiple zones, complex schedules

Advanced Controllers:

Smart controllers:

  • Cost: $200-500
  • Features: Weather adjustment, smartphone control
  • Connectivity: WiFi enabled for remote management
  • Best for: Professional operations, frequent travelers

Computer-based systems:

  • Cost: $500-2,000
  • Features: Full automation, data logging, multiple sensors
  • Integration: Can control heating, cooling, ventilation
  • Best for: Commercial operations, research facilities

Sensor Integration

Soil Moisture Sensors:

Tensiometers:

  • Cost: $50-100 each
  • Function: Measure soil water tension
  • Range: Works in most soil types
  • Maintenance: Requires periodic refilling

Electronic moisture sensors:

  • Cost: $80-200 each
  • Function: Measure soil moisture content
  • Range: Calibrated for specific growing media
  • Integration: Can connect to automatic controllers

Environmental Sensors:

Temperature/humidity sensors:

  • Cost: $100-300
  • Function: Monitor greenhouse climate
  • Integration: Adjust irrigation based on environmental conditions
  • Benefits: Prevent overwatering during humid periods

Light sensors:

  • Cost: $150-400
  • Function: Measure daily light integral (DLI)
  • Application: Adjust watering based on photosynthesis levels
  • Benefits: Optimize water use efficiency

Smart Irrigation Features

Weather-Based Adjustment:

Evapotranspiration (ET) controllers:

  • Automatically adjust watering based on weather data
  • Reduce irrigation during cool, cloudy periods
  • Increase watering during hot, windy conditions
  • Can save 20-40% water compared to fixed schedules

Smartphone Apps:

Remote monitoring:

  • Check system status from anywhere
  • Receive alerts for system problems
  • Manual override for special situations
  • View historical usage data

Data analysis:

  • Track water usage patterns
  • Identify optimization opportunities
  • Monitor plant growth correlations
  • Export data for record keeping

Maintenance and Troubleshooting

Regular Maintenance Schedule

Weekly Tasks:

  • [ ] Check timer operation and schedules
  • [ ] Inspect plants for water stress signs
  • [ ] Verify all emitters are functioning
  • [ ] Clean clogged emitters as needed

Monthly Tasks:

  • [ ] Clean screen filter
  • [ ] Check system pressure
  • [ ] Inspect tubing for damage
  • [ ] Test automatic valves and controls

Seasonal Tasks:

  • [ ] Replace filter cartridges
  • [ ] Flush main lines
  • [ ] Calibrate sensors
  • [ ] Update watering schedules for season

Annual Tasks:

  • [ ] Complete system inspection
  • [ ] Replace worn components
  • [ ] Update control programming
  • [ ] Plan system improvements

Common Problems and Solutions

Problem: Low Water Pressure

Symptoms:

  • Emitters not flowing properly
  • Uneven distribution across zones
  • System takes too long to complete cycles

Solutions:

  1. Clean filters: Clogged filters reduce pressure
  2. Check for leaks: Fix all connection leaks
  3. Reduce zone size: Split large zones into smaller ones
  4. Upgrade main lines: Use larger diameter tubing
  5. Install booster pump: For severely low pressure situations

Problem: Emitter Clogging

Symptoms:

  • Individual emitters not flowing
  • Dry spots in irrigated areas
  • White mineral deposits on emitters

Solutions:

  1. Improve filtration: Add or upgrade filters
  2. Treat water: Use water treatment for hard water
  3. Regular cleaning: Soak emitters in vinegar solution
  4. Upgrade emitters: Use self-cleaning or pressure-compensating types
  5. Flush lines: Regular flushing prevents buildup

Problem: Overwatering

Symptoms:

  • Yellowing leaves, especially lower leaves
  • Fungal growth on soil surface
  • Slow plant growth despite adequate nutrition

Solutions:

  1. Reduce frequency: Water less often but for longer periods
  2. Check drainage: Improve container or bed drainage
  3. Install moisture sensors: Automate based on actual soil moisture
  4. Adjust for weather: Reduce watering during cool, humid periods
  5. Improve air circulation: Better ventilation reduces water needs

Problem: System Not Starting

Symptoms:

  • Timer runs but no water flows
  • Manual operation doesn't work
  • No response from automatic valves

Solutions:

  1. Check power: Verify timer has power (replace batteries)
  2. Test valves: Manual operation of automatic valves
  3. Check wiring: Inspect connections between timer and valves
  4. Water source: Verify main water valve is open
  5. Backflow preventer: Check if device is functioning properly

Economic Analysis: Irrigation ROI

Water Cost Savings

Manual vs. Automated Watering:

Manual watering (8x12 greenhouse):

  • Time: 30 minutes daily = 180 hours annually
  • Labor value: $15/hour = $2,700 annually
  • Water usage: 50% higher than automated systems
  • Water cost: Additional $200-400 annually

Automated drip system:

  • Installation cost: $300-600
  • Annual maintenance: $50-100
  • Time savings: $2,700 annually
  • Water savings: $200-400 annually
  • Payback period: 3-6 months

Yield Improvements

Production Increases from Proper Irrigation:

Consistent moisture:

  • Tomatoes: 25-40% yield increase
  • Lettuce: 30-50% more uniform heads
  • Herbs: 40-60% faster growth
  • Overall: 25-35% average yield improvement

Quality improvements:

  • Reduced stress: Better flavor and nutrition
  • Uniform size: More marketable produce
  • Extended harvest: Longer productive periods
  • Reduced losses: 90% reduction in water-stress deaths

System Cost Comparison (16x20 greenhouse)

| System Type | Initial Cost | Annual Operating | 5-Year Total | Water Efficiency | | ----------------- | ------------ | ---------------- | ------------ | ---------------- | | Manual watering | $50 | $3,200 | $16,050 | 60% | | Basic drip system | $400 | $1,800 | $9,400 | 90% | | Automated drip | $800 | $1,600 | $8,800 | 92% | | Smart controller | $1,200 | $1,400 | $8,200 | 95% |

Winner: Smart controller system provides best 5-year value despite higher initial cost.

Advanced Irrigation Strategies

Deficit Irrigation

Concept: Controlled water stress during specific growth stages to improve fruit quality and water efficiency.

Applications:

  • Tomatoes: Reduce watering during ripening for better flavor
  • Herbs: Stress plants to concentrate essential oils
  • Fruiting crops: Improve sugar content through controlled stress

Implementation:

  1. Identify stress periods: When slight stress benefits crop
  2. Monitor closely: Watch for excessive stress signs
  3. Use sensors: Soil moisture monitoring critical
  4. Start conservatively: Begin with 10-20% reduction

Pulse Irrigation

Concept: Short, frequent watering cycles instead of long, infrequent ones.

Benefits:

  • Better infiltration: Prevents runoff on heavy soils
  • Improved uniformity: More even distribution
  • Reduced evaporation: Less surface water loss
  • Root development: Encourages extensive root systems

Example Schedule: Instead of 30 minutes once daily:

  • 10 minutes, 3 times daily (morning, midday, evening)
  • Or 5 minutes, 6 times daily for very porous media

Precision Irrigation

Concept: Individual plant monitoring and watering based on specific needs.

Technologies:

  • Individual plant sensors: Monitor each plant separately
  • Variable rate emitters: Different flow rates for different plants
  • AI-driven systems: Machine learning optimizes watering
  • Computer vision: Cameras monitor plant stress indicators

Cost-Benefit:

  • High initial cost: $50-200 per plant monitoring
  • Significant benefits: 15-25% additional yield improvements
  • Best applications: High-value crops, research operations

Future of Greenhouse Irrigation

Emerging Technologies

Internet of Things (IoT) Integration:

  • Wireless sensors: No-wire installation throughout greenhouse
  • Cloud data storage: Historical data analysis and trends
  • Machine learning: Predictive watering based on patterns
  • Integration: Combine with climate, lighting, and nutrition control

Precision Agriculture:

  • Plant-specific irrigation: Customized watering for each plant
  • Growth stage adaptation: Automatic adjustment for development stage
  • Stress optimization: Beneficial stress application for quality improvement
  • Yield prediction: Correlation between irrigation and expected harvest

Next Steps: Implementing Your Irrigation System

  1. Assess current needs: Use our Water Usage Calculator to determine requirements
  2. Design your system: Download our Irrigation Planning Worksheet
  3. Compare costs: Get quotes from multiple suppliers and installers
  4. Start simple: Begin with basic drip system, upgrade over time
  5. Monitor and optimize: Track performance and make improvements

Ready to upgrade your watering system? Our certified irrigation specialists provide free consultations to design the perfect system for your greenhouse. Schedule a consultation or contact us for personalized recommendations.

Struggling with current irrigation problems? Join our community of 12,000+ growers in our Facebook Group for real-world advice and troubleshooting help from experienced greenhouse owners.