TYPES OF RECHARGE
Dry Wells

What is a Dry Well?

A dry well is an underground structure that captures runoff from roof tops and surrounding areas and diverts it to the local groundwater table.

How does a Dry Well Work?

Water flows through the dry well under the influence of gravity. A dry well receives water from one or more entry pipes or channels at its top. Roof leaders connect directly into the dry well, which may be either an excavated pit uniformly filled with gravel, rip-rap  or rubble, wrapped in geo-textile or a prefabricated storage chamber or pipe segment. Dry wells then discharge the stored runoff via infiltration into the surrounding soils. In the event that the dry well is overwhelmed in an intense storm event, a surcharge pipe or a connection to larger infiltration area will ensure that additional runoff is safely removed. It is very important that the dry well be properly designed and installed, with careful consideration of the elevation of local groundwater. A dry well that is installed too close to the surface may freeze in very cold weather. One installed below the existing or anticipated groundwater level would tend to fill with groundwater and not contribute to raising groundwater levels.

What are the Advantages and Disadvantages of Dry Wells?

Advantages:
  • Increase groundwater recharge
  • Reduce volume of storm water
  • Underground structure that does not devalue property
  • Can last up to 30 yrs. with proper maintenance

Disadvantages:
  • Difficult to install in low permeable soils
  • If not properly maintained, clogged dry wells must be refurbished or replaced
  • If not properly engineered a dry well could do more harm than good. i.e. flood adjacent property(s)

What are some different types of Dry Wells?

There are many different types of dry wells. Here are some examples: