Residential tap water, often referred to as kitchen water, is subject to rigorous treatment and testing before it reaches a home’s service line. The general safety of this water is well-established by federal and state regulations, which aim to protect public health from a wide range of contaminants. However, the water’s quality can change significantly after it leaves the municipal system and travels through the specific plumbing within a house. Understanding the journey of water from the source to your glass is the first step in addressing concerns about its overall safety for drinking and cooking.
Baseline Safety and Regulatory Standards
In the United States, the quality of public water is governed by the Safe Drinking Water Act (SDWA), which establishes minimum standards for all public water systems. The U.S. Environmental Protection Agency (EPA) sets legally enforceable limits on over 90 contaminants, including chemicals, microorganisms, and radionuclides. These standards, known as National Primary Drinking Water Regulations, require water systems to treat and monitor the supply to protect public health.
States are authorized to implement and enforce these federal regulations, often setting standards that are at least as stringent as the EPA’s requirements. Public water suppliers must regularly test the water and report results to regulatory bodies, ensuring the water meets strict safety thresholds before it enters the distribution network. The regulatory framework ensures that the water delivered from the treatment plant is initially safe for consumption.
The Critical Difference Between Hot and Cold Water
When seeking water for consumption, it is recommended to use only cold tap water. Hot water is stored in a water heater tank, where its elevated temperature increases the rate at which metals and other substances dissolve from the tank lining, pipes, and fixtures. This means hot water is more likely to contain higher concentrations of contaminants like lead and copper.
The warm environment of a water heater, particularly if the temperature is set below 140°F (60°C), can also promote the growth of microorganisms. Bacteria, such as Legionella, thrive in lukewarm water conditions and can accumulate in the tank. Using hot tap water for cooking or drinking is not advised, even if boiled afterward, because boiling concentrates non-volatile contaminants like heavy metals. Therefore, cold water should always be drawn and then heated on the stove or in a kettle if warm water is needed.
How Household Plumbing Affects Water Quality
The most common cause of water quality degradation occurs after the water leaves the municipal main and enters the private plumbing system. Residential pipes and fixtures are the primary source for the leaching of heavy metals. Older homes, particularly those built before 1986, may have lead service lines or used lead solder to join copper pipes, a practice banned in 1991.
Even in newer construction, brass faucets and fixtures, which can legally contain small amounts of lead, can release the metal into the water supply. The water’s chemistry plays a significant role in this process. Water that is slightly acidic or has a low mineral content is considered corrosive and can dissolve pipe materials more readily. This corrosion releases metals like lead and copper into standing water, with concentrations highest after the water has been stagnant for several hours. Copper corrosion can also lead to a metallic taste and blue-green staining in sinks.
Testing Methods and Filtration Solutions
The most reliable first step is to have the water tested by a certified laboratory. These professional labs provide the most accurate analysis and can test for a wide spectrum of contaminants, including heavy metals and bacteria. The cost for a comprehensive lab test typically ranges from $20 to $250, depending on the number of contaminants screened. Less expensive at-home kits offer an initial screening for basic parameters like pH and chlorine, but they lack the precision of laboratory analysis.
Once a water analysis is complete, an appropriate filtration solution can be chosen to address specific issues. Activated carbon filters, commonly found in pitcher and faucet-mount systems, are effective at removing chlorine, improving taste and odor, and reducing certain organic chemicals. For the removal of heavy metals like lead, an under-sink reverse osmosis system is often the most effective option. A simple habit that reduces exposure to contaminants that have leached from pipes is flushing the tap for 15 to 30 seconds after the water has been sitting unused for many hours.