Experiencing a sudden, unpleasant change in the flavor of drinking water is a common and often unsettling phenomenon. This abrupt shift in palatability raises immediate concerns about quality and safety. The cause can range from large-scale changes at the municipal treatment level to localized issues within a home’s plumbing system. Understanding the potential origins is the first step toward identifying the cause and taking appropriate action.
Changes in Municipal Water Source or Treatment
The taste of tap water often reflects temporary adjustments made by the local water utility. A frequent cause is an increase in disinfectants, such as chlorine or chloramine. This occurs during routine system maintenance, like seasonal flushing, or when the utility switches to a more potent free chlorine application. People closer to the treatment plant may notice this taste more strongly because the disinfectant has not yet had time to dissipate.
Environmental conditions also contribute significantly, particularly in systems drawing from surface water sources like lakes or reservoirs. Seasonal warming can trigger an algal bloom, causing cyanobacteria to multiply rapidly. These organisms produce compounds like geosmin and methylisoborneol (MIB), which impart a distinct earthy, musty, or fishy flavor. While these flavors are highly noticeable and unpleasant, the water is typically still safe to drink.
Sudden infrastructure problems, such as a major water main break, can introduce new tastes and odors. A drop in pressure can allow surrounding materials to infiltrate the system, sometimes resulting in a salty or sewage-like taste. Changes in water flow can also temporarily stir up sediment, leading to brief periods of off-tasting water that reaches homes.
Issues Within Your Home Plumbing and Appliances
If the water tastes bad only at your taps, the source is likely localized to your plumbing or appliances. A metallic or bitter taste often points to the leaching of trace minerals from older pipes or fixtures. Water stagnant in galvanized iron, copper, or brass pipes overnight dissolves small amounts of metal, making the flavor strongest when first turning on the tap. This is accelerated if the water supply is naturally acidic.
The rotten egg smell is caused by hydrogen sulfide gas. If this odor is only noticeable in the hot water, the source is the water heater tank. Sulfate-reducing bacteria thrive in the warm, dark environment, converting sulfates into hydrogen sulfide gas. The sacrificial anode rod, installed to prevent tank corrosion, can sometimes accelerate this chemical reaction.
A musty or moldy taste can originate from a neglected water filter, such as an expired carbon cartridge. Over time, the filter media can harbor bacterial growth or become saturated with impurities, transferring an unpleasant flavor back into the filtered water. Flexible plastic hoses connecting fixtures can also contribute a chemical or plastic-like flavor, especially if they are new.
When the Problem Is Your Own Sense of Taste
Sometimes, the water is unchanged, and the bad flavor originates from an alteration in chemosensory perception, known as dysgeusia. This can make the pure taste of water seem metallic, bitter, or foul. Illnesses affecting the respiratory system, such as a cold or flu, can significantly distort taste and smell.
A change in medication is another frequent cause of distorted water flavor perception. Many prescription and over-the-counter drugs can produce a metallic or bitter aftertaste. These chemical compounds can be excreted into the saliva, or they can directly interfere with the sensory signaling pathways of the taste buds. This altered perception can be sudden, especially when starting a new drug or changing a dosage.
Conditions causing dry mouth (xerostomia) can also amplify the perception of subtle flavors. Saliva neutralizes tastes and washes away compounds, so reduced flow leaves the mouth more sensitive to trace minerals or disinfectants. If the unpleasant flavor is persistent across multiple beverages, a physiological cause is more probable than a water supply problem.
Determining Safety and Next Steps
When water suddenly tastes bad, determine if the flavor is an aesthetic issue or a potential safety hazard. Faint chlorine or mineral tastes are typically benign, suggesting utility changes or plumbing stagnation. However, a strong chemical, petroleum, or sewage-like taste warrants immediate caution, and the water should not be consumed.
To quickly isolate the problem, follow these steps:
- Run the cold water tap for a few minutes to flush out water sitting in the pipes.
- If the bad taste persists, check the hot water separately; if only the hot water is affected, the water heater is the clear suspect.
- Ask a neighbor if they are experiencing the same issue, which helps determine if the problem is system-wide or limited to your residence.
If the problem appears to be related to the municipal supply, contact the local water utility, as they can provide information on any recent system maintenance or environmental events that could affect taste. For localized plumbing issues, a professional plumber may be needed to inspect the water heater or check for corroded pipes. If the cause is not obvious, or if a potentially hazardous taste is present, having the water tested by a certified laboratory can provide a definitive analysis of its content.