This article, written by the American Ground Water Trust was originally published in THE AMERICAN WELL OWNER, 2001, Number 4]


The cap that covers the well in your back yard was not put there just for decoration. It is actually a very important piece of your well water system. A properly installed cap prevents the well from becoming contaminated from surface pollutants.

If a well cover is not sealed properly, insects (such as earwigs) can crawl through gaps around casing or through unscreened vents and form nests inside the well. Bacteria can reach unhealthy levels when enough cumulative dead bodies and droppings from the residing insects fall into the well water. The well cap usually includes a vented screen so that the pressure difference between the inside and outside of the well casing may be equalized as water is pumped out of the well. Without a vent, a vacuum will be created within the well casing when the water level falls [during pumping or drought] that may draw unwanted contaminants and debris into the well. Watertight caps are available for areas prone to flooding and not subject to significant changes in well water levels.

A properly sealed well cap will also keep out surface water and contaminants from entering the well. Surface water can encounter many different kinds of pollutants such as lawn pesticides and animal feces and easily transport them. Unfortunately, bacteria and other contaminants are not easily detected by taste or smell. Laboratory testing is the surest method of determining if any unsafe levels are present. Tests should be taken annually regardless of whether your well cap is properly sealed because well water can become contaminated from many different sources.

A correctly constructed well cover has a watertight gasket between the casing and the cap and fine mesh screens covering the vents. Certain types of well caps in addition also have an access cover that requires a separate gasket. In some cases the cap will be made out of plastic. Usually these caps use solvent weld in place of a gasket for the watertight seal (plastic caps are mainly used to cover plastic casing).

Regardless of what type of well cap you have, maintenance is essential in order to ensure that the well remains sealed. Gaskets should be checked on a regular basis as recommended by the manufacturer. Be sure to avoid damage from snowplows and lawnmowers. Taking time to routinely inspect your well in order to prevent possible contamination is a small price to pay for clean safe drinking water.

For more information on well caps go to: www.watersystemscouncil.org

[© American Ground Water Trust. This article may be reprinted for non-commercial educational purposes provided it is used in its entirety and that reference is made to its source as an article in THE AMERICAN WELL OWNER, 2001, Number 4]