Dry Well Sizing Calculator

Calculate the required dry well volume for your drainage area and compare costs across gravel pit, prefab chamber, and infiltration crate systems.

Drainage Area (sq ft)

Design Storm Depth (in)

Soil Perc Rate (in/hr)

Desired Drain Time (hrs)

Pricing (edit to match local rates)

Gravel ($/cu yd)

Chamber ($/each)

Crate ($/each)

Fabric ($/sq ft)

Runoff Volume

624 gal

83.3 cu ft

Required Storage

83.3 cu ft

624 gallons

Gravel Pit Cost

$469.38

7.7 cu yd gravel

Suggested Pit Size

6' x 6' x 6'

7.7 cu yd gravel

Material Breakdown — Gravel Pit

Purchase Option	Quantity	Est. Cost
Drainage GravelBest value	7.7 cu yd	$424.38
Landscape Fabric	180 sq ft	$45.00

Cost Comparison Across Well Types

Purchase Option	Quantity	Est. Cost
Gravel PitBest value	7.7 cu yd gravel	$469.38
Prefab Chamber	13 chambers	$1,648.51
Infiltration Crate	18 crates	$1,611.50

Best value: Gravel Pit at $469.38A gravel pit dry well is the most affordable option and easy to build with basic tools. The tradeoff is a larger excavation footprint due to gravel's ~40% void ratio.

Minimum distance from foundation: 10 ftAlways locate dry wells at least 10 feet from any building foundation. Many local codes require even greater setbacks. Verify with your local building department before installation.

Drain time may exceed targetAt the specified soil percolation rate (1 in/hr), the stored water may not fully drain within 24 hours. Consider a larger well, improving the soil, or adding an overflow outlet.

This is an estimate for sizing and material costs only. Actual requirements depend on soil type, water table depth, local codes, and site conditions. A percolation test is recommended before installation. Always consult local building codes and consider hiring a professional for engineering design.