What are they?
Soakaway pits, also known as dry wells, are underground systems used to allow rainfall to infiltrate into the ground. The downspout is connected to an underground pit lined with gravel or coarse materials. The layers of gravel help to slow down the infiltration of water and also to clean and purify it naturally. Soakaway pits require relatively clean water with some pre-filtering to prevent debris from clogging the system, so they usually only accept rainfall from roofs through a downspout.
How do they work?
Stormwater is directed to the soakaway pit by a downspout and is stored in the empty spaces between the stones. The water then slowly filters down through the gravel and into the surrounding soil providing water to plant roots and recharging groundwater supply.
What are the Benefits?
- Once installed below ground, the system requires minimal maintenance and avoids stormwater ponding on your property.
- The underground location is ideal for medium sized properties as pits are dug deep into the ground and take up little surface space.
- The gravel helps to remove fine sediments and pollution.
A few Tips...
- Soakaway pits work well with other stormwater management systems to deal with overflow.
- Soakaway pits work well in cold climates if they are built below the frost line.
- See the Do It Yourself (DIY) section to learn about Infiltration Rates on your property and how to measure and size the system.
- Soakaway pits should be designed by a qualified professional. It is not advisable to construct one on your own because of ground water flow implications. Explain and provide details to a manufacturer for proper installation.
- A similar system is a manufactured plastic underground chamber, common in areas that produce substantial and more polluted runoff, like parking lots. These systems do not use gravel to clean the water, but have special filters. Plastic manufactured chambers take up smaller areas underground compared to traditional gravel pits.
Professional installation is required. Installed soakaway pits can cost from $300 to $500 for existing properties.
- Minimal maintenance to the pit itself is required.
- It is important to maintain clear flows into the pit or chamber to prevent clogging by leaves and debris. Downspouts connected to the pits should be cleaned and fitted with filters to prevent leaf matter from entering.
- Inspection by a professional can be performed if the pit is not draining properly.
For basic information to get started on designing and sizing a soakaway pit, see Do-It-Yourself in the Library.