Tap water purification removes unwanted contaminants to improve safety, taste, or odor. While municipal systems meet safety standards, local water quality varies due to aging infrastructure or environmental factors. Many seek purification for aesthetic reasons, such as eliminating chlorine taste, or out of concern for contaminants like lead that enter the supply after treatment. Understanding the available methods allows for an informed decision on the best approach for a household’s needs. This guide covers accessible methods, ranging from emergency techniques to advanced home systems.
Immediate and Emergency Purification Techniques
In situations where the water supply is compromised or unavailable, such as during a power outage or natural disaster, quick sanitation methods are necessary. The most certain way to kill disease-causing microorganisms, including bacteria, viruses, and parasites, is through boiling. Water should be brought to a full, rolling boil for at least one minute. At elevations above 6,500 feet, boiling for three minutes is recommended due to the lower boiling point of water. Boiling effectively inactivates pathogens but does not remove chemical contaminants or heavy metals.
When boiling is not an option, chemical disinfection using unscented household bleach (containing 5.25% to 8.25% sodium hypochlorite) can be used. For clear water, add eight drops (or about 1/8 teaspoon) of bleach per one gallon of water. The mixture must be stirred thoroughly and allowed to stand for 30 minutes before consumption to ensure adequate contact time. If the water is cloudy, the dosage should be doubled, and the water ideally filtered first to remove suspended particles. A faint chlorine taste can be reduced by aerating the water, such as by pouring it between two clean containers.
Standard Household Filtration Systems
For daily aesthetic improvement and removal of common chemical contaminants, standard household filtration systems are the most popular choice. These systems primarily rely on two mechanisms: adsorption and mechanical filtration. They are commonly found in simple formats like pitcher filters, faucet-mounted units, and refrigerator dispensers, offering an affordable and easy solution.
The core of these systems is activated carbon filtration, which works through adsorption. Carbon, derived from materials like coconut shells, is treated to create a vast network of tiny pores, significantly increasing its surface area. As water passes through, chemical contaminants like chlorine, volatile organic compounds (VOCs), and compounds causing poor taste and odor adhere to this porous surface. This mechanism is highly effective for improving palatability.
These systems also incorporate mechanical filtration, which removes suspended particles. Mechanical filters, often made of fibrous material, act as a sieve, trapping particles like rust, sand, and sediment. This process is rated by a micron size, indicating the smallest particle diameter the filter can capture. While effective for removing sediment and improving clarity, standard carbon filters do not significantly reduce dissolved inorganic substances, such as minerals, salts, or nitrates.
Advanced Water Purification Technologies
Advanced purification technologies target a wider array of persistent contaminants, dissolved solids, and heavy minerals that standard filtration cannot address. These methods involve complex scientific principles and require significant investment and installation complexity. Reverse Osmosis (RO) is one such method that goes beyond simple adsorption and straining.
The RO process utilizes a semi-permeable membrane and applied pressure to separate water molecules from almost all other substances. Pressure forces the water through the membrane, which has microscopic pores large enough for water molecules but too small for nearly all dissolved solids. This includes heavy metals like lead and arsenic, nitrates, and salts. The rejected contaminants are flushed away in a separate stream, often referred to as “waste water.” Because the delicate RO membrane can be damaged by chlorine and sediment, most home RO systems include pre-filters—typically sediment and carbon—to protect the main membrane.
Water distillation is a purification method based on a phase change, mimicking the natural process of rain. The water is heated to boiling, turning it into pure steam, which leaves behind a residue of inorganic compounds, heavy metals, and non-volatile organic molecules. The steam is then captured and cooled, condensing back into purified liquid water. Distillation is highly effective at removing minerals and virtually all biological contaminants. However, it may not efficiently remove volatile organic chemicals (VOCs) that have a boiling point close to or lower than water, as these can vaporize and condense along with the steam.
Matching Purification Methods to Specific Needs
Choosing the correct purification method depends on the specific contaminants present, the desired water quality, and practical considerations like cost and installation. The first step should always be to have the local water quality tested by a certified laboratory, especially if contaminants like lead or nitrates are a concern. Testing provides a clear picture of what needs to be removed, preventing unnecessary expense on systems that do not address the actual problem.
If the primary goal is simply to improve the taste and odor of safe municipal water, a low-cost, low-complexity carbon-based pitcher or faucet filter offers an excellent solution. These point-of-use systems are easy to maintain and replace. However, for serious health contaminants like heavy metals, high total dissolved solids (TDS), or nitrates, a more permanent, high-complexity solution is required.
Reverse Osmosis or distillation systems are best suited for these complex issues. RO is highly effective against dissolved solids and heavy metals, but it is a complex, multi-stage system with higher upfront and maintenance costs and higher water usage. Distillation produces nearly mineral-free water and is also highly effective against non-volatile contaminants. The final decision should balance the high efficacy and cost of advanced systems against the convenience and lower cost of standard filtration, based on the water test results.