Dry well

[2][3] Dry wells are excavated pits that may be filled with aggregate or air and are often lined with a perforated casing.

[7][8] Simple dry wells consist of a pit filled with gravel, riprap, rubble, or other debris.

Such pits resist collapse but do not have much storage capacity because their interior volume is mostly filled by stone.

A more advanced dry well defines a large interior storage volume by a concrete or plastic chamber with perforated sides and bottom.

A covered pit that disposes of the water component of sewage by the same principle as a dry well is called a cesspool.