Dry well

If storm water races from your yard and across the next lawn over after every heavy rain—washing out a flowerbed and cutting a ditch along the way—you could probably expect a knock on the door from one very disgruntled neighbor. But neighbor issues would be the least of your problems. With uncontrolled storm water, you can expect erosion and localized flooding time and time again. Dry wells are just one means by which homeowners can collect and control storm water runoff. They are not suitable for everyone, however, so read on to determine if it’s the best drainage solution for your yard. 

When Dry Wells Can Help 

Imagine a large paved parking lot. Before the parking lot was there, falling rain soaked evenly into the soil. Now when it rains, the water can no longer drain, so it runs to the lowest area on the parking lot. Before long, water pools, and—if the developer did not make provisions to divert the water in a controlled manner—it will run over the curb and erode the soil beyond. 

The same principle is at work in your own yard: Rain falls on your roof, drains to the gutters, and then rushes out of the downspouts to wherever it can drain in the soil. Even water from a gentle rain can build up force as it exits the downspouts. 

That’s where a dry well comes in. A successful installation harnesses gravity to direct water toward the lowest point in the yard, where a dry well has been buried. This gives runoff water a place to collect until it gradually dissipates into the soil, instead of cascading across the lawn surface and pooling in depressed areas. 

Note that while dry wells typically collect runoff from the roof, they can also be used to relocate gray water (the relatively clean water wasted by sinks, baths, washing machines, and dishwashers).

Is a Dry Well Right for Your Property?

In some developments, homeowners may be required to install one or more dry wells to reduce the impact on municipal storm drains. If dry wells aren’t mandated where you live, you can use soil testing along with advice from your local building authority to help determine whether a dry well would help your setup. 

The most important factor in determining whether your yard could benefit from this in-ground installation is your soil’s infiltration rate, or how quickly water can be completely absorbed into soil. To calculate this rate, you’ll conduct a percolation (perc) test in your yard—a process that involves digging a hole (or numerous holes), filling them with water, and then recording the rate at which the water seeps into the ground a spot where the water drains away quickly might be a good candidate for a dry well; while homeowners who have heavy clay soil on the property and slower drainage will likely need to find a different option for moving storm water. 

Sizing and Materials 

If local ordinances do not regulate the size and number of dry wells, it’s standard practice to install one for each downspout. Additional dry wells may be necessary if elements of your landscape are creating a drainage problem, such as runoff from a driveway or large patio. 

Ideally, dry wells should be large enough to collect runoff without overflowing in typical rain events. Depending on the average amount of storm water you need to control, you can choose install a dry well that’s as small as a couple feet in depth and diameter or as large as