The short answer
The Fundamental Problem: Precipitation Rate
Spray heads and rotors apply water at completely different rates:
- Spray heads: 1.5 to 2.0 inches per hour
- Rotors: 0.4 to 0.8 inches per hour
That is a 3 to 4x difference. For real runtime numbers across DFW spray and rotor zones, see our DFW seasonal watering schedule.
When you run a mixed zone for 20 minutes:
- Spray areas receive about 0.5 to 0.7 inches, so they are overwatered and drowning.
- Rotor areas receive about 0.15 to 0.25 inches, so they are drought-stressed.
The spray areas drown while the rotor areas stay dry. No runtime adjustment fixes this.
Why "Upgrading" to MP Rotators Makes It Worse
MP Rotators and R-VANs are multi-stream rotating nozzles that fit into spray bodies. They are excellent when used correctly, as a complete zone conversion.
MP Rotators apply water at about 0.4 inches per hour, similar to rotors, not sprays.
If you replace three spray heads with MP Rotators and leave the rest as sprays, you now have the same precipitation mismatch.
MP Rotators only work when an entire zone is converted.
What Proper Zone Design Looks Like
Each zone should contain one head type with matched precipitation rates. Your controller programming can then be tuned to that single rate:
- Only spray heads with matched precipitation rates, or
- Only rotors with matched precipitation rates, or
- Only MP Rotators and R-VANs with matched precipitation rates, or
- Only drip irrigation
Never mix types.
When to Call a Pro
If you have inherited a mixed zone, options include:
- Splitting the zone into two (requires adding a valve and wiring)
- Converting all heads to the same type (full zone replacement)
- Redesigning head placement (spacing and coverage optimization)
None are DIY repairs.
An irrigation audit is the best way to identify mixed zones and measure exactly how uneven the distribution is before committing to a fix. From there, a professional can handle the full sprinkler repair and zone redesign.