Well water can get dirty when there is a lack of maintenance in the well system, which can lead to deterioration. Wells may have to be cleaned, and because some people never do this, the water can become dirty.
This can happen in only a few years if the well is not properly cleaned. Too much iron, manganese and hydrogen sulfide gas can cause well water to be contaminated. People that have this problem may notice an unpleasant smell coming from their water system. This can become a significant problem, filling a home with a sewer-like or sulfurous scent.
Wells can also become contaminated with bacteria, like coliform and other bacteria types. A heterotrophic plate count can be used to find out how much bacteria is in the water. While this test can't be very specific, it does give a good summation of the state of the well.
When bacteria becomes a problem, wells must be cleaned and decontaminated. If this isn't done, the well becomes a breeding ground for the bacteria. The bacteria can get into clothes that are washed, as well as plates, appliances and on people's bodies when they try to take showers. This isn't just dirty, it's unhealthy, as these bacteria can cause diseases.