Why Letting Tap Water Sit Improves Taste
Municipal water systems add disinfectants, primarily chlorine or chloramine, to kill harmful bacteria and other pathogens. This process makes tap water safe for consumption, but it can leave a chemical taste or odor that many people find unpleasant. Letting tap water sit out is a simple, cost-free method to address this.
The Science of Dechlorination
Chlorine is a volatile chemical, meaning it has a tendency to evaporate, or "gas off," when exposed to the open air. This process can be accelerated by increasing the surface area of the water or raising its temperature. When you pour tap water into a glass or pitcher and let it stand, the chlorine gradually dissipates into the atmosphere. The result is water with a more neutral, cleaner taste and smell.
The Effect of Chloramine
While chlorine is effectively removed by letting water sit, many municipalities now use a more stable disinfectant called chloramine (chlorine combined with ammonia). Chloramine does not evaporate easily and will not dissipate simply by being left out. If your water supplier uses chloramine and you still notice a chemical taste, a carbon filtration system is the most effective solution for removal. You can contact your local water authority to find out which disinfectant they use.
The Risks of Stale Water
While letting tap water sit for a short time can be beneficial for taste, leaving it for too long, especially in an uncovered container, introduces new risks. As the protective chlorine evaporates, the water becomes susceptible to re-contamination from the surrounding environment.
Bacterial Growth
Once the chlorine is gone, the water's natural defense against microbial life is removed. Bacteria from the air, your hands, or other sources can enter the water and begin to multiply. This risk is amplified in warmer temperatures, which provide an ideal breeding ground for microorganisms. If you drink directly from a container, your mouth's natural bacteria can also be backwashed into the water, creating a prime environment for germ growth. While the bacteria from your own mouth are unlikely to make you sick, sharing a bottle can be problematic.
Taste Changes and Contaminants
Even if a glass of water isn't teeming with bacteria, it can still lose its pleasantness. The absorption of carbon dioxide from the air can slightly alter the water's pH, leading to a flatter, less crisp taste. An uncovered glass can also collect dust, debris, and absorb odors from its environment, such as cooking fumes or cleaning product scents.
Best Practices for Safe and Fresh Water
To ensure your drinking water is both safe and great-tasting, consider these best practices.
Proper Storage Techniques
- Use the right container: Opt for food-grade glass or stainless steel pitchers and bottles, which are non-permeable and won't leach chemicals.
- Cover it up: Always use a container with a lid to prevent airborne particles and bacteria from contaminating the water.
- Keep it cool: Store filled pitchers or bottles in the refrigerator. The cold temperature significantly slows down bacterial growth, allowing the water to stay fresh longer.
- Limit standing time: For water left out in an open glass, consume it within 12 hours. If refrigerated in a sealed container, it can be safely stored for up to 24 hours, after which the minimal chlorine residue is likely gone.
Other Effective Methods
- Use a water filter: For an instant and more comprehensive solution, a water filter pitcher or under-sink system can remove chlorine, chloramine, and a wider range of contaminants.
- Flush the tap: Run the cold water for 15-30 seconds after it has gone unused for several hours. This flushes out water that has been sitting stagnant in the pipes, which can accumulate minerals and trace amounts of metal.
- Regularly clean containers: Wash reusable bottles, pitchers, and glasses with hot, soapy water every day to prevent biofilm and bacterial buildup.
Comparing Water Treatment and Storage Methods
| Method | Primary Purpose | How It Works | Best For | Considerations |
|---|---|---|---|---|
| Letting it Sit | Improve taste | Allows volatile chlorine to evaporate | Removing chlorine taste and odor | Doesn't remove chloramine; risk of bacterial growth |
| Refrigeration | Storage & taste | Slows bacterial growth; masks some flavors | Longer-term storage (24+ hours) | Keep sealed to prevent odor absorption |
| Boiling | Disinfection | Kills most microorganisms; evaporates chlorine | Emergency purification, making flat water | Can concentrate other contaminants; energy-intensive |
| Activated Carbon Filter | Filtration | Adsorbs chlorine, VOCs, and some heavy metals | Improving taste and removing chemicals | Doesn't remove all contaminants; requires maintenance |
| Reverse Osmosis (RO) | Advanced purification | Forces water through a semi-permeable membrane | Comprehensive contaminant removal | Can remove beneficial minerals; more complex system |
Conclusion
For most people, a glass of tap water left out overnight is perfectly safe to drink, though the taste may be flatter due to chlorine dissipation. However, to ensure the freshest and safest water, it is best to be mindful of storage times and conditions. Consuming water within 12-24 hours and keeping it covered in a clean container, preferably refrigerated, are simple, effective habits. For those seeking immediate taste improvement or more extensive purification, a water filter is a worthwhile investment. Always prioritize using clean, food-grade containers and regularly checking your local water quality reports through resources like the EPA website.
