Drywells, Infiltration Systems, & You

Drywells are underground structures designed to collect and disperse stormwater runoff from roofs, driveways, and other surfaces into permeable soils below. Drywells come in two forms: a rock-filled drywell, and a formal drywell. A rock-filled drywell consists of a large, excavated pit filled with gravel or rock. A formal drywell consists of perforated concrete rings. They allow rainwater to percolate slowly into the surrounding soil, effectively recharging groundwater and controlling surface water runoff. Drywells can also help reduce pollution by filtering contaminants before they reach waterways. They are an eco-friendly and sustainable solution for managing stormwater runoff and preserving water quality.

Drywell rings, also known as formal drywell systems, are prefabricated concrete structures designed to create underground reservoirs for stormwater storage and infiltration. These range in size from 24” to 48” and larger in diameter and are made in 1ft, 2ft, and 4ft sections. Normally, a formal drywell system is used 6-8ft below the surface in residential applications. These rings are typically interconnected to form a larger empty space, allowing rainwater to collect and gradually infiltrate into the surrounding soil. Drywell rings provide an efficient and customizable solution for managing stormwater runoff. They are commonly used in residential, commercial, and municipal stormwater management projects where the soil permits.

Rock-filled drywells are typically installed at depths ranging from 4 to 6 feet. Functioning as a more informal variant of traditional drywells, they consist of a deep pit filled with drain rock. This approach proves to be more cost-effective and is particularly suitable for shallower spaces. When a property doesn't necessitate as much infiltration or water storage as a formal drywell provides, rock-filled drywells serve as an excellent alternative.

All our drywells are equipped with an overflow mechanism to ensure optimal functionality. Typically, this overflow takes the form of a bubbler at the surface. This precautionary feature is essential for addressing rare instances when the system may become overwhelmed. Instead of backing up towards your home, the bubbler facilitates the safe dispersal of any excess water onto the ground's surface. Serving as a backup to the infiltration process, this bubbler ensures reliable and efficient drainage, even during extreme weather conditions.

While both drywells and infiltration systems are used for managing stormwater runoff, they differ in their design, function, and application:

An infiltration system is a network of interconnected underground structures, such as trenches, chambers, or modular units, designed to collect and infiltrate stormwater runoff into the soil. Infiltrators, also known as infiltration trenches, are designed for shallow installation, typically reaching depths of 2 to 4 feet. These systems are particularly well-suited for properties with soil compositions that have better draining upper layers above clay substrates. By spreading water out across a larger surface area, infiltration trenches facilitate enhanced infiltration into the soil. Compared to traditional drywells, infiltrators offer a greater volume capacity, making them an efficient choice for managing stormwater runoff and promoting groundwater recharge in these areas.

Infiltration systems are used in a variety of settings, including residential, commercial, and municipal projects. They are particularly suitable for larger developments with extensive impervious surfaces and high volumes of runoff.

Installing a drywell requires careful planning and excavation to ensure proper sizing and placement. Once installed, regular maintenance is minimal, typically consisting of removal of sediment buildup in the sediment trap or leaf screen installed to downspouts that feed into the drywell itself. If a drywell quits, a scope can be fed through the lines to determine the problem.

The installation of a drywell typically involves several key steps:

1. Site Assessment: A drainage professional will assess your property to determine the best location for the drywell based on factors such as soil type, groundwater levels, proximity to buildings, and local regulations.
2. Excavation: Once the location is determined, the area for the drywell is excavated to the appropriate depth and size based on the volume of stormwater runoff to be managed.
3. Testing: Once excavated, the drywell hole may be tested to ensure proper functioning and infiltration rates.
4. Preparation: The bottom of the excavation is leveled, and any sharp rocks or debris are removed to ensure a stable base for the drywell.
5. Drywell Placement: The drywell, which may be a prefabricated concrete structure or drain rock, will be placed in the excavated site. 
6. Connection: Downspouts or drainage pipes from gutters, driveways, or other impermeable surfaces are connected to the drywell to direct stormwater runoff into the system.
7. Backfilling: The area around the drywell is backfilled with gravel or rock to provide structural support and promote infiltration of water into the surrounding soil.
8. Covering: A cover or lid is installed on top of the drywell to prevent debris from entering.

It's important to note that the installation process may vary depending on site-specific conditions, local regulations, and the type of drywell system being installed. Hiring a qualified drainage professional or contractor is recommended to ensure that the drywell is installed correctly and effectively addresses your property's drainage needs.

You may need a drywell if you are experiencing any of the following issues related to stormwater runoff and drainage:

Flooding: If your property frequently floods during heavy rainfall or you notice standing water pooling in certain areas, a drywell may be able to help alleviate this issue by capturing and infiltrating excess water into the soil.

Waterlogged Soil or Soil Erosion: If your soil becomes waterlogged and saturated after rainstorms, it may indicate poor drainage conditions. A drywell can provide an effective solution for draining excess water from the soil, preventing waterlogging, and promoting healthier plant growth. Erosion may also be helped by reducing the volume and velocity of runoff entering vulnerable areas.

Standing Water around Downspouts: If you frequently observe standing water pooling around your downspouts or along the foundation of your home, it may indicate that your current drainage system is overwhelmed.

If you're experiencing any of these issues or others, it's recommended to consult with a drainage professional or contractor to assess your property's drainage needs and determine if a drywell is the right solution for you. They can evaluate your site conditions, soil type, and local regulations to design and install a drywell system that effectively addresses your drainage challenges.