What is a well vent, and do I need one on my water well?

A well vent is a component that functions to prevent a vacuum, release gases such as methane or hydrogen sulfide, and help gases escape from the well vent. Some states, such as Minnesota, require new wells to have a vented cap or cover. However, an older well may not be vented.

To vent a well, you can choose from a variety of vented well caps or use a separate down-turned vent. It is important for vented caps or covers to be installed on wells to properly vent them and prevent the entry of flood water, contaminants, insects, and small animals​. Part of your routine well maintenance should include making sure that the screen on your well vent is in place and undamaged.

When your well pump operates and draws down the static water level, it can create a vacuum inside the well casing. The well vent allows equalizing air into the casing, preventing any pump performance issues a vacuum may cause.

Proper venting at the well head is also essential for gas removal. For instance, if methane gas, which is lighter than air, is present in your well it can exit through a vented well cap. When the well is recovering after pumping, the upward movement of water in the casing pushes accumulated gases, out the top of the well. If large amounts of combustible gases are present, the well vent should terminate above head level to avoid ignition risks.