How Dry Wells Work
Stormwater can cause costly flooding and damaging erosion to properties. To prevent this, downspouts and drains redirect rainfall and runoff from non-absorbent surfaces (like a roof and driveway) into a concrete galley or dry well that has been buried underground. The perforated unit(s) allow water to dissipate slowly and drain out of the holes, into the ground. Each of the galleys featured in this video hold 300 gallons of water—giving the homeowner a whopping total of 2400 gallons worth of water storage. Additionally, thanks to the stone foundation, this system will be able to process and drain even more water than that. A job this scale is expensive—about $25,000—but it wasn’t a surprise to the homeowners. Because the new garage build reduced the amount of available ground that typically helps absorb rainfall, the need for a dry well had been part of the original design.
Steps for Installing a Dry Well
Considerations that Affect the Job:
Percolation Test: Also known as a “perc test,” this test determines how fast water drains into the soil. The faster the water drains into the soil within a certain amount of time, the better location for a dry well. Calculating Impervious Surfaces: The more non-absorbent surfaces that a building site has, like driveways and roof surfaces, the larger the dry well system required to effectively manage all the additional runoff and avoid flooding and erosion. Capability for a Worst Case Scenario: This particular system is large enough to handle a 100-year storm—a storm that can expect to drop 9” of rain over 24 hours. A project this size is better left to the professionals, but if there is an area of your home or yard that pools and floods during rainstorms, it is possible to build and install a simple dry well for your home.
