What 30 inches per hour actually measures

Thirty inches per hour is the vertical permeability of the turf backing under lab conditions. Real performance depends on the whole system: turf, infill, base, subgrade soil, slope, edge conditions, and any subsurface drains. The turf sheet is rarely the bottleneck. Poor base design and lack of outlets usually are.

When 30 in/hr is enough

  • Moderate rainfall climates where peak storm intensity is around 1 to 2 in/hr.
  • A clean, open graded crushed stone base that does not trap fines.
  • Base thickness of 3 to 5 inches sized to your soil and loads.
  • Finished grade set to a 1 to 2 percent slope toward a discharge point.
  • Open edges or perimeter drains so water has a way out.

When to target 50 to 100 in/hr

  • Coastal, tropical, or storm heavy regions with frequent cloudbursts.
  • Very flat sites or low pockets that tend to pond.
  • Tight clay subgrades with slow percolation.
  • High traffic sports, dog runs, or putting greens that need fast recovery.
  • Projects with strict local stormwater requirements.

Quick reality check with numbers

Example

Lawn area: 1,000 sq ft. Rainfall intensity: 2 in/hr. Rain volume on the lawn each hour is 1,000 sq ft × 2 in = 166.7 cubic ft, about 1,246 gallons. A turf rated at 30 in/hr over 1,000 sq ft can pass up to 2,500 cubic ft per hour in the lab, about 18,700 gallons. The turf backing is not the limiter. Your base, soil, slope, and outlets set the pace.

What to verify on site

  • Subgrade percolation. Clay soils may require thicker base or underdrains.
  • Positive slope. Aim for 1 to 2 percent to a safe discharge point.
  • Edge conditions. Avoid fully sealed borders unless you add drains or weeps.
  • Local design storm. Use NOAA Atlas 14 or local code guidance for target intensity.

Build the system to move water

Base design

  • Install 3 to 5 inches of angular, open graded stone such as No. 57 clean rock.
  • Place a nonwoven geotextile between soil and base to block fines migration.
  • Compact in thin lifts to a firm yet permeable base.

Slope and shaping

  • Set final grade at 1 to 2 percent away from structures.
  • Feather transitions to sidewalks and drains so water does not stall.

Outlets and underdrains

  • Provide a daylight outlet, catch basin, or French drain where water can exit.
  • On tight soils, add perforated pipe within the base to accelerate removal.

Product selection tips

  • Match turf drainage rating to climate: 30 to 50 in/hr for most lawns, 50 to 100 in/hr for storm heavy regions.
  • Confirm backing perforation pattern for uniform flow.
  • Select infills that resist clogging and keep dust and organics off the surface.

Maintenance that preserves drainage

  • Blow or brush off leaves, dust, and pet hair that can bind infill.
  • Top up or refresh infill if it compacts or migrates.
  • Keep edges, basins, and outlets clear before major storms.

Regional guidance

  • Pacific and Mid Atlantic: 40 to 60 in/hr with robust base and clear outlets.
  • Gulf and tropical storm zones: 60 to 100 in/hr plus underdrains on tight soils.
  • Arid regions with monsoon bursts: 40 to 80 in/hr and strong grading to swales.
  • Interior clay soils: prioritize thicker base and drains even at 50 to 100 in/hr.

Get a spec you can build with

Share your site size, soil, and climate. FusionTurf will return a drainage spec and bill of materials you can install with confidence.