Filtered water is water that has undergone a process to remove undesired substances found in the source supply. This process is intended to improve the water’s taste, odor, purity, and safety compared to standard municipal tap water. While public water systems are regulated to meet safety standards, filtration offers an additional layer of processing aimed at reducing trace contaminants. Determining if filtered water is beneficial depends on the specific impurities removed and the trade-offs involved.
Common Impurities Found in Tap Water
Municipal water supplies contain several categories of substances that filtration systems are designed to address. One major group is chemical additives, primarily chlorine or chloramines, which are intentionally introduced during treatment to disinfect the water and eliminate disease-causing microbes. These disinfectants are highly effective, yet their presence contributes to the distinct taste and smell often associated with tap water.
A second category includes environmental pollutants that enter the water source through various pathways. These encompass pesticides and herbicides from agricultural runoff, nitrates from fertilizers, and industrial chemicals like per- and polyfluoroalkyl substances (PFAS). Such contaminants can seep into groundwater or surface water, persisting due to their chemical stability and raising potential health concerns.
The third significant group is heavy metals, which often enter the water supply after it leaves the treatment plant. Lead and copper typically leach into the water from aging infrastructure, including service lines, plumbing fixtures, and solders within older homes. Other metals like arsenic and cadmium can be naturally occurring in the source water or result from industrial waste.
Health Advantages of Removing Water Contaminants
The removal of contaminants offers several direct health and quality-of-life benefits. Filtering out the disinfectant agents and their byproducts can reduce long-term exposure to harmful compounds. When chlorine or chloramines interact with natural organic matter, they form disinfection byproducts (DBPs) like trihalomethanes (THMs) and haloacetic acids (HAAs).
Exposure to these DBPs has been associated with long-term health risks, including certain cancers and adverse reproductive outcomes. Carbon filtration, even in simple pitcher or tap-mounted form, is effective at reducing these chemical byproducts. Removing chemicals like chlorine also immediately improves the water’s taste and odor, which encourages individuals to drink more water and maintain better hydration.
Furthermore, filtration provides a layer of defense against neurotoxic substances like lead and copper. Lead is a known developmental hazard, and filtering water to reduce its concentration is important for vulnerable populations, such as infants, young children, and pregnant women. By removing heavy metals that accumulate in the body over time, filtration minimizes the risk of chronic toxicity, kidney damage, and nervous system issues.
Essential Minerals and Filtration Trade-Offs
While filtration offers considerable advantages, it also introduces certain trade-offs, depending on the technology used. Highly aggressive filtration methods, such as Reverse Osmosis (RO) or distillation, remove nearly all total dissolved solids (TDS), including beneficial minerals. The process strips away naturally occurring electrolytes like calcium and magnesium, which contribute to dietary intake.
Although most people obtain the majority of these minerals from food, the contribution from water can still be significant, especially for individuals whose diets may be borderline deficient. Studies show that RO water can remove 92–99% of calcium and magnesium. This leads to concerns about potential effects on cardiovascular and skeletal health if consumed exclusively over a long period. Some systems address this by incorporating a remineralization stage to reintroduce these compounds.
Maintenance of the filtration system is an important consideration. If filters are not replaced according to the manufacturer’s schedule, they become saturated with trapped organic matter and contaminants. This accumulation creates an environment where bacteria can multiply, potentially allowing the growth of microorganisms and the formation of a biofilm. An old filter can begin to re-release trapped contaminants or bacteria, resulting in water quality worse than the original tap supply.
Matching Filtration Methods to Specific Needs
Different filtration technologies target different impurity groups, making the choice of system dependent on the specific water quality issue. Activated carbon filters use adsorption to capture organic compounds, chlorine, and disinfection byproducts. These systems are effective for enhancing taste and odor, but they do not remove dissolved salts, minerals, or microbial contaminants.
Reverse Osmosis (RO) systems utilize a semi-permeable membrane with fine pores to physically block nearly all dissolved solids. RO is the most comprehensive method, excelling at removing heavy metals, salts, nitrates, and even some bacteria and viruses. The trade-off is that RO is slower, generates wastewater, and requires a storage tank.
For microbiological safety, ultraviolet (UV) purification or boiling is necessary, as most carbon and RO systems are designed for chemical removal. A UV system uses light at a specific wavelength (254 nanometers) to inactivate 99.9% of bacteria and viruses by disrupting their DNA. UV treatment is instantaneous and chemical-free, but it does not remove sediments, chemicals, or heavy metals, so it is often used in combination with other filter types.