Irrigation Pipe Sizing Calculator
Size mainline and lateral pipes for landscape irrigation systems
Water Supply
From water meter or well
Zone Requirements
Pipe Run
+ uphill, - downhill
Pipe Requirements
Recommended Pipe Size
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Velocity
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Zone Flow Rate
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Friction Loss
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Elevation Loss/Gain
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Pressure at Last Head
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Tip: Keep velocity under 5 fps for mainlines and 7 fps for laterals to minimize water hammer.
Flow Capacity by Pipe Size
| Pipe Size | Max GPM (5 fps) | Max GPM (7 fps) |
|---|---|---|
| 1/2" | 4 | 6 |
| 3/4" | 8 | 11 |
| 1" | 13 | 18 |
| 1-1/4" | 22 | 31 |
| 1-1/2" | 30 | 42 |
| 2" | 50 | 70 |
Design Guidelines
- Maintain 20-30 PSI at sprinkler heads
- Size mainline for total simultaneous flow
- Size laterals for single zone flow
- Allow 5% safety margin on pressure
- Use swing joints at sprinkler heads
Sprinkler Head Flow Rates
| Head Type | Typical GPM | Operating PSI | Radius |
|---|---|---|---|
| Spray Heads | 1-3 GPM | 25-30 PSI | 4-15 ft |
| Rotor Heads | 2-6 GPM | 30-50 PSI | 15-50 ft |
| MP Rotator | 0.5-1.5 GPM | 25-45 PSI | 8-35 ft |
| Drip Emitters | 0.5-2 GPH | 15-30 PSI | Point source |
| Impact Heads | 3-8 GPM | 40-60 PSI | 30-80 ft |