When tap water tastes distinctly like dirt, it can be a surprising and unsettling experience. This common phenomenon has a scientific basis, typically stemming from naturally occurring compounds or issues within the water distribution system. Understanding the reasons behind this earthy taste can help demystify what is happening with your drinking water.
The Main Culprits
The primary cause of an earthy or musty taste in tap water is the presence of two naturally occurring organic compounds: geosmin and 2-methylisoborneol (MIB). These compounds are byproducts of certain types of algae, specifically cyanobacteria (blue-green algae), and some bacteria. They are released into water sources such as reservoirs, lakes, and rivers, particularly during algal blooms or when these organisms decay.
Algal blooms tend to occur more frequently in warmer months, including spring, summer, and early fall, when water temperatures are elevated and nutrient levels are sufficient to support rapid growth. Humans possess an exceptionally sensitive ability to detect geosmin and MIB. Even in extremely small concentrations, these compounds can be perceived, making the “dirt” taste quite noticeable. Water utilities routinely monitor for these compounds, but their presence can still lead to taste and odor complaints.
Safety Concerns
A common concern when water tastes unusual is its safety for consumption. Although geosmin and MIB produce an unpleasant taste and odor, they are generally considered harmless to human health at the concentrations typically found in drinking water. Water treatment plants are equipped to handle these compounds and ensure that the water meets safety standards before it reaches your tap.
While the earthy taste from geosmin and MIB does not usually indicate a health risk, it can cause concern about water quality. If, however, the water exhibits other unusual characteristics, such as discoloration or an extremely strong or unfamiliar smell, or if anyone experiences illness after consumption, it warrants further investigation beyond just the earthy taste. The primary issue with these compounds is aesthetic, affecting the palatability of the water rather than its safety.
Other Causes
Beyond geosmin and MIB, several other factors can contribute to an earthy or musty taste in tap water. Sediment or particulate matter, such as rust or mineral deposits like iron and manganese, can sometimes enter the water supply. This is more common in homes with older plumbing or well water systems.
Decaying organic matter within a water source can also impart an earthy flavor. This can occur during events like lake turnover, where deeper, oxygen-depleted water containing decomposed material mixes with surface water. Additionally, issues within household plumbing, such as mold, mildew, or bacterial growth in faucet aerators, showerheads, or drains, can affect the water’s taste as it passes through.
What You Can Do
When your tap water tastes earthy, there are several practical steps you can take. A good first action is to contact your local water utility to report the issue; they are often aware of such events and can provide information or solutions. Often, flushing your household pipes by running cold water taps for a few minutes can help clear stagnant water and any accumulated sediment.
Cleaning household plumbing fixtures is also beneficial, particularly faucet aerators, where sediment and bacterial films can accumulate. For a more consistent solution, installing a water filter, especially one with activated carbon, can effectively remove geosmin and MIB, significantly improving the taste and odor of your water. While chilling water or adding a slice of lemon can temporarily mask the taste, boiling water will not remove these compounds and may even intensify the odor.