Quick answer: Spray nozzles on a header should be spaced so adjacent patterns overlap — as a general starting guideline, 25–33% overlap between adjacent spray patterns is a common target used in header design to avoid gaps caused by natural thinning at the edge of each nozzle’s pattern. Exact spacing depends on spray angle, mounting height, and nozzle type, and should be verified against the specific nozzle’s published coverage data.
Why Overlap Is Necessary, Not Optional
Every spray pattern is denser in the center and thins toward the edges — this is true for full cone, flat fan, and hollow cone patterns alike. If nozzles are spaced edge-to-edge with zero overlap, the thinning zones from adjacent nozzles combine into a visible low-coverage stripe or gap rather than blending into uniform coverage. Deliberate overlap compensates for this natural edge thinning.
Calculating a Starting Spacing Value
Using the coverage-width formula from what is spray angle (Coverage width = 2 × Distance × tan(Angle ÷ 2)), a practical starting spacing is:
Nozzle spacing ≈ Coverage width × (1 − Overlap %)
Worked example: A flat fan nozzle produces an 18-inch coverage width at the mounting distance in use. Targeting 30% overlap:
Spacing ≈ 18 × (1 − 0.30) = 18 × 0.70 = ≈ 12.6 inches between nozzles
This gives a starting point for header layout, which should then be confirmed with a physical spray distribution check once installed, since real-world overlap behavior can vary from the theoretical calculation.
Flat Fan vs. Full Cone Spacing Logic
| Nozzle Type | Overlap Pattern | Design Consideration |
|---|---|---|
| Flat fan | Linear — overlap along a single line of nozzles | Common on cleaning/washing headers; spacing is largely one-dimensional |
| Full cone | Radial — overlap in a grid or staggered layout | Common on cooling/dust suppression headers; spacing must account for coverage in two dimensions, often staggered row-to-row |
| Hollow cone | Radial with a dry center | Requires closer attention to overlap since the pattern center itself is naturally under-covered |
Practical Recommendations
Start from the nozzle’s published coverage data at your actual mounting distance, not a generic industry rule of thumb, since spray angle and distance are specific to each installation. After installation, a basic spray distribution check (catch trays or a simple visual/flow check across the covered area) is the most reliable way to confirm the calculated spacing actually delivers uniform coverage in practice, since factors like pressure variation across the header can still create unevenness even with correct geometric spacing.
Common Mistakes
Spacing nozzles based only on their rated coverage diameter with zero planned overlap is one of the most common design errors, producing visible low-coverage lines between nozzles. Another frequent mistake is copying a spacing value from a different nozzle model or a different mounting distance without recalculating — coverage width changes with both spray angle and distance, so spacing that worked for one setup doesn’t automatically transfer to another.
FAQ
How much overlap should spray nozzles have?
A commonly used starting guideline is 25–33% overlap between adjacent spray patterns, though the ideal value depends on nozzle type, spray angle, and mounting distance.
How far apart should spray nozzles be spaced on a header?
Spacing should be calculated from the nozzle’s coverage width at your mounting distance, then reduced by your target overlap percentage — not based on a fixed distance that ignores spray angle and mounting height.
Does spacing differ between flat fan and full cone nozzles?
Yes. Flat fan nozzles typically need linear overlap along one axis, while full cone nozzles need overlap in two dimensions, often requiring a staggered grid layout for even coverage.
Related reading: what is spray angle, high pressure misting nozzle spacing, and why is my spray pattern uneven. Ready to review coverage data? View spray nozzle product specifications.