"Class V wells are used to inject non-hazardous fluids underground. Most Class V wells are used to dispose of wastes into or above underground sources of drinking water and can pose a threat to ground water quality, if not managed properly. This website provides information on recognizing the different types of Class V wells and the threats they pose. This website also provides information about:

• what you need to do if you own or operate one of these well types;
  
• how you can protect ground water; and where you can go, and
  
• who you can talk to if you want additional information.

Most Class V wells are shallow disposal systems that depend on gravity to drain fluids directly in the ground. There are over 20 well subtypes that fall into the Class V category and these wells are used by individuals and businesses to inject a variety of non-hazardous fluids underground. EPA estimates that there are more than 650,000 Class V wells in operation nationwide. Most of these Class V wells are unsophisticated shallow disposal systems that include storm water drainage wells, cesspools, and septic system leach fields. However, the Class V well category also includes more complex wells that are typically deeper and often used at commercial or industrial facilities.

Other more sophisticated Class V well types could include aquifer storage and recovery wells or geothermal electric power wells that are used to inject geothermal fluids extracted from subsurface hydrothermal systems.
Complex Class V wells also include wells that are used for pilot geologic sequestration (GS) projects that are experimental in nature. On 12/10/10, the Agency  finalized regulations for GS projects. These new regulations include the creation of a new class of well, Class VI. EPA understands that some of the wells permitted as Class V experimental technology wells may no longer be used for experimental purposes.

Following the final rule, Class V wells that are not being used for experimental purposes must be re-permitted as Class VI wells and will be subject to Class VI requirements. 

Regardless of the use of a Class V well, owners and operators are responsible for protecting underlying ground water from contamination by the fluids they inject. Ninety percent of America's public water systems draw their water from ground water sources."