How long does a dry well last?

A properly installed and maintained dry well typically lasts 15–30 years. Lifespan depends heavily on upstream sediment protection—systems with good catch basins and clean gutter runoff last longest. Without maintenance, clogging from sediment and fines can reduce a dry well's effectiveness within 5–10 years.

How deep should a dry well be?

Most residential dry wells are installed 3–5 feet deep, though depth depends on soil conditions and water table height. The bottom of the dry well must be at least 2 feet above the seasonal high water table, and ideally 3–4 feet above it. Always perform a percolation test at the planned installation depth before digging.

Do dry wells work in clay soil?

Dry wells generally do not work well in heavy clay soil. Clay has a percolation rate below 0.5 inches per hour, meaning the well fills up faster than it can drain. In clay soils, alternatives like French drains, infiltration trenches with engineered soil, or surface grading solutions are usually more effective.

Do I need a permit to install a dry well?

Permit requirements vary by jurisdiction. Many municipalities require a permit for dry well installation, especially for systems exceeding a certain size or those handling runoff from large impervious areas. Some areas prohibit dry wells entirely near wellhead protection zones or contaminated sites. Always check with your local building department before installation.

How far should a dry well be from the house foundation?

Most building codes require a minimum of 10 feet between a dry well and a building foundation, though some jurisdictions require 20 feet. This setback prevents infiltrated water from migrating toward the foundation and causing hydrostatic pressure or basement seepage. Greater distances are always better when space allows.

What size dry well do I need for my downspout?

Sizing depends on the roof area draining to that downspout and your local rainfall intensity. As a rough guideline, every 500 square feet of roof area in a moderate rainfall region (2 inches per hour design storm) generates about 625 gallons of runoff. A single small prefabricated unit (30–50 gallons) is rarely sufficient; most downspout applications require multiple connected units or a large gravel-filled pit.

Dry Wells Explained: When They Work and When They Fail

Learn when a dry well works for stormwater drainage and when it fails. Expert guide covers installation, soil types, sizing, and common mistakes to avoid.

By Low Point Labs

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