That second design worked perfectly.
How do you measure your property for irrigation planning?
Start with a measuring wheel and graph paper. Walk the entire perimeter of your property. Mark every building, tree, and driveway.
Note the location of your water source. Measure the static water pressure at the outdoor spigot. Use a $15 pressure gauge from the hardware store.
It dropped to 48 PSI. That difference of 14 PSI matters for design.
Create a scaled drawing on grid paper. One square equals 10 feet works well. Mark all hardscapes, flower beds, and lawn areas separately.
Measure the distance from your water source to each zone location. It is surprisingly accurate for large properties.
3 acres on paper. 31 acres. The extra detail helped me plan head placement.
Shady areas need less water. Full sun areas need more. support/irrigation-parts-and-components-reference/) will help you select materials for each zone.
How many zones do you need for a 5,000 sq ft lawn?
You need three to four zones for a 5,000 sq ft lawn. Each zone handles roughly 1,200 to 1,800 square feet. A rotor head covers about 30 to 35 feet radius.
That is roughly 3,000 square feet per head at full circle. But you need head-to-head coverage. That brings coverage down to about 1,500 square feet per head.
If your flow rate is 12 GPM at 50 PSI, each rotor uses 3 to 4 GPM. That gives you 3 to 4 heads per zone. Each zone covers 1,200 to 1,600 square feet.
His water supply delivered 10 GPM at 55 PSI. Zone 1 had four rotors covering the front.
Zone 2 had three rotors for the side yard. Zone 3 had four rotors for the back. Each zone ran for 25 minutes per cycle.
Total water usage was about 2,000 gallons per week. His previous system used 4,500 gallons. The proper zoning cut his usage by more than half.
Zone count is about matching flow rate to area. It is not about covering every square foot at once.
How do you calculate pipe size for each zone?
Calculate total GPM for the zone first. Add up the flow rate of every head on that zone. Then use a friction loss chart to find the right pipe size.
Velocities above 5 FPS cause water hammer. 5 FPS. That is safe.
8 FPS. That is too fast.
9 FPS. That is perfect.
Use Hunter’s online friction loss calculator. It is free and easy to use. Enter the pipe size, material, length, and flow.
It tells you the pressure loss. 5 PSI loss maximum. The remaining pressure must be enough for the sprinkler heads.
Most rotors need 35 to 45 PSI at the nozzle. Spray heads need 20 to 30 PSI. support/irrigation-controllers-complete-guide/) to match your zone design.
What is head-to-head coverage and why does it matter?
Head-to-head coverage means each sprinkler sprays to the next sprinkler. The spray from one head reaches the adjacent head. This creates overlapping coverage with no dry spots.
The rotors claimed 50-foot radius. The grass in those strips died every August.
Proper spacing means heads are 50% to 60% of their rated diameter apart. A rotor with a 40-foot radius goes no more than 24 feet from the next head. This overlap ensures even water distribution.
The edges of each spray pattern mix with the next. No spot gets too little water. No spot gets too much.
It adds more heads but saves water. More heads mean more zones in some cases. Each zone needs 30 to 50 PSI at the head.
Flow per zone ranges from 6 to 14 GPM. The extra heads pay for themselves in even coverage. support/irrigation-pumps-selection-installation-guide/) must match these zone requirements.
Think about wind too. Wind blows water away from the target. Head-to-head coverage compensates for wind loss.
The overlapping spray fills the gaps. With proper head-to-head spacing, that drops to 5%.
The math works out every time. Design for overlap. Your lawn will stay green through July. Mine does now.
