Dry Well for Yard Runoff: A Gravel Pit for Roof Water
A dry well for yard runoff is a small pit filled with gravel. It takes water from a roof downspout plus lets it soak into the soil instead of running across the yard.
The short answer
Washington State University Extension describes a dry well as a pit lined with fabric plus filled with 1.5 to 3 inch gravel. It suits roof water with little sediment. Soil around it must drain well. It should empty within 48 hours. Place it at least 10 feet from foundations.
How does a dry well work?
WSU notes directing downspouts into a dry well helps water soak into the surrounding soil. It also stops roof water picking up surface sediment. Large storms may need an overflow.
| Feature | Guideline | Source |
|---|---|---|
| Fill | 1.5 to 3 inch gravel | WSU |
| Lining | Fabric or weed cloth | WSU |
| Drain time | Within 48 hours | WSU |
| From foundations | At least 10 feet | WSU |
Source: Washington State University Extension.
Is a dry well the same as a rain garden?
No. UConn NEMO notes a rain garden is a shallow planted dip with mulch. A typical home rain garden is 50 to 100 square feet. A dry well sits underground without plants.
How do downspouts feed a dry well?
University of Arizona Extension shows roof water running through a gutter plus downspout onto a splash pad, then into a basin to soak in. A dry well moves that water below ground.
How to: step by step
- Locate where the downspout drains.
- Pick a spot 10 feet from the house.
- Check that the soil drains well.
- Dig the pit plus line it with fabric.
- Fill it with washed gravel.
- Add an overflow for big storms.
Troubleshooting
Water lingers for days: slow soil. WSU notes it should drain in 48 hours.
Silt in the pit: muddy runoff. WSU advises roof water only.
Yard still washes out: bare soil. UGA notes organic matter helps water soak in.
For yard planning see garden microclimates plus planning an outdoor garden layout. Read overwatering. Kind Seed Co also stocks cannabis seeds.
Sources
- Rain gardens, UConn CT NEMO Program
- Landscape management practices to optimize passive rainwater harvesting and plant health (AZ1916), University of Arizona Cooperative Extension
- Controlling soil erosion improves vegetable gardens, University of Georgia Extension
- Improving drainage, Washington State University Extension, Clark County
FAQ
How far should a dry well be from the house?
WSU Extension advises placing a dry well at least 10 feet from building foundations.
How fast should a dry well drain?
WSU notes a dry well should drain completely into the soil within 48 hours of the rain.
What gravel goes in a dry well?
WSU describes 1.5 to 3 inch gravel in a pit lined with fabric or weed cloth.
Is a dry well the same as a rain garden?
No. UConn NEMO notes a rain garden is a shallow planted dip. A dry well is a buried gravel pit.
Does a dry well need maintenance?
WSU notes the dry well should be placed where it can be reached easily for maintenance.
