Water purification involves removing contaminants to improve the safety, taste, and odor of the water flowing from the sink. The need for purification varies widely, depending on the local water source and the age of the home’s plumbing. Choosing the right method, from temporary disinfection to permanent filtration systems, depends on the specific water quality issue a homeowner is attempting to solve. The most effective strategy begins with accurately identifying the substances present in the water supply.
Temporary and Emergency Purification Methods
When a public water system issues a “boil water” advisory or during a power outage, simple methods can quickly disinfect water for short-term use. Boiling remains the most reliable method for neutralizing biological threats, as the intense heat destroys waterborne pathogens. A rolling boil for at least one minute at sea level is sufficient to inactivate bacteria, viruses, and parasites like Giardia and Cryptosporidium. At altitudes above 6,500 feet, the recommended boiling time increases to three minutes to compensate for the lower boiling point of water.
Boiling does not remove chemical contaminants and can actually concentrate non-volatile substances like heavy metals and nitrates as the water evaporates. If boiling is not possible, chemical disinfection using unscented liquid household bleach (5.25% to 8.25% sodium hypochlorite) is an alternative. Adding eight drops (or 1/8 teaspoon) of bleach per gallon of water and allowing it to sit for 30 minutes can kill most bacteria and viruses. This chemical approach is ineffective against Cryptosporidium cysts and should be doubled for visibly cloudy water.
Convenient Point-of-Use Filtration
For daily improvement in taste and odor, point-of-use filtration offers a simple solution for a single tap. Common devices include pitcher filters, refrigerator filters, and faucet-mounted units, all relying on activated carbon filtration. Activated carbon works through adsorption, where organic compounds and contaminants adhere to the vast surface area of the porous carbon material.
Pitcher filters are portable and require no installation, but they use gravity to slowly filter the water, limiting the available volume. Faucet-mounted filters connect directly to the tap and use water pressure to provide an instant, continuous flow through a small cartridge. Both types are effective at reducing chlorine, which improves taste and smell, and can filter out some volatile organic compounds (VOCs) and certain heavy metals. These systems are considered aesthetic filters because they do not remove the high percentage of dissolved solids, nitrates, or fluoride that more complex systems can.
Comprehensive Installed Purification Systems
For the highest level of water purity, systems installed under the sink or plumbed into the water line offer superior contaminant removal. Reverse Osmosis (RO) systems force water under pressure through a semi-permeable membrane with microscopic pores. This membrane rejects up to 99% of dissolved inorganic solids, including heavy metals like lead and arsenic, nitrates, and fluoride.
A consequence of RO purification is the removal of beneficial minerals like calcium and magnesium, which can result in a flat taste and slightly acidic water. Many modern systems include a final remineralization stage to reintroduce these minerals, improving the flavor and balancing the pH. A drawback of RO is the production of wastewater, as a volume of water is used to flush the concentrated contaminants down the drain.
Distillation units offer an alternative high-purity method by heating water until it vaporizes and then condensing the steam back into purified liquid, leaving virtually all inorganic compounds and microorganisms behind. While effective against heavy metals and bacteria, certain organic compounds with a lower boiling point than water, such as benzene, may vaporize alongside the water and re-contaminate the final product. For those concerned primarily with taste and chlorine reduction, a high-capacity under-sink carbon block filter provides a robust flow rate and longer filter life than a faucet unit, often lasting six to twelve months.
Assessing Current Water Quality
Selecting the correct purification method requires knowing what contaminants are present in the water supply. Public water customers should first consult their annual Consumer Confidence Report (CCR), mandated by the U.S. Environmental Protection Agency (EPA). The CCR details the water source and the levels of detected contaminants, and is often mailed to homeowners or available on the local utility’s website.
If concerns remain, especially for private well owners or those with older plumbing, water testing is necessary. Do-it-yourself (DIY) home kits offer a quick, affordable screening for basic parameters like pH, chlorine, and hardness, often using color-matching strips. However, these kits may lack precision and often only indicate the presence or absence of a contaminant rather than the exact concentration.
For a precise understanding of health-related contaminants like lead, arsenic, or bacteria, testing should be performed by a certified laboratory. Laboratory analysis provides a comprehensive, high-accuracy evaluation, giving the specific concentrations needed to determine if a contaminant exceeds regulatory limits. If a lab test reveals lead or arsenic, a membrane-based solution like Reverse Osmosis or distillation is necessary, as simpler carbon filters are insufficient to remove these substances to safe levels.