- Damage to the well casing or cap: If the casing is broken or cracked, water percolating through shallow soil or rock near the surface can reach your well. Likewise, a damaged well cap can admit surface water, small animals or insects along with bacteria, fungi and other pathogens.
- Improperly built well: In some cases, well casings are too short to protect the quality of the water. The EPA states that the casing should extend at least 18 feet underground. A casing that does not go deep enough could allow surface water to percolate through soil and enter the well. The casing should also extend at least 12 inches above the ground to keep out surface water.
- Buried well cap: With the casing extending at least 12 inches above ground and a tight-fitting well cap, surface contamination is minimal. But some homeowners bury their well caps for aesthetic reasons. Any surface water along with the chemicals, salts or organic matter it contains will now be able to contaminate the water supply. This problem is common with older wells.
- Poor placement of well: A well must be placed in an area free from brush or overhanging trees and not in an area where water will flow toward it during heavy rainstorms. Because salting of nearby roads can also infiltrate a well, it should not be near a highway, road or driveway.
- Contaminants from nearby lakes: Private wells near homes or ponds may have special problems because of the proximity of these bodies of water. Lakes and ponds often have high levels of fungi and iron bacteria which can leak into nearby wells. Lakes used for recreation can be contaminated with gasoline ingredients such as MTBE, benzene, ethylbenzene, toluene or xylenes. These chemicals can seep through soil or bedrock and make their way into the aquifer and wells.
- Naturally-occurring substances: Just because a substance occurs naturally in the soil or bedrock around a private well doesn’t mean that you want it in your well water. Contaminants such as arsenic, iron, radon, radium and uranium can make their way into your water from the surrounding bedrock.
- Industrial, manufacturing, mining, military or agricultural activities: Any of these operations can release toxins into the soil or water supply. Contaminants like nitrates, hydrocarbons, pesticides or toxic metals can be released into the soil and then make their way into the aquifer. It’s possible for these toxins to travel a mile or more underground.
From the outside, wells look like closed systems that completely protect the quality of your well water. But like any other household structure, they can age or suffer damage from outside causes. In some cases, the well may have even been built improperly so that contamination becomes inevitable. It’s a good idea to know how different contaminants get into your well water so you know what problems to look for. Here are some of the most typical reasons your water could contain too many undesirable substances that can cause problems for your health and your home.