Filtered water is water that has undergone a physical or chemical process to remove impurities, a practice increasingly popular in homes around the world. Source water, whether from a municipal system or a private well, contains various substances, both harmless and potentially harmful. Filtration methods are designed to selectively reduce or eliminate these components, yielding water that is cleaner and often better tasting. The core question is whether this extra step provides verifiable health advantages.
Enhancing Water Safety Through Contaminant Removal
The primary health justification for filtering drinking water lies in the reduction of harmful contaminants that can be present even in treated public supplies. Long-term exposure to certain substances, even those meeting regulatory standards, can be linked to chronic health issues. Filtration directly addresses this concern by acting as an additional barrier against unwanted compounds before consumption.
Lead, a potent neurotoxin, is a significant concern because it often leaches into water from older service lines or household plumbing. Exposure to lead, especially in children, can cause developmental issues, while in adults it has been associated with increased blood pressure and kidney problems. Filtering the water is a proven method to reduce this risk at the point of use.
Trihalomethanes (THMs) form when chlorine, used as a disinfectant, reacts with natural organic matter in the water. Long-term ingestion of THMs has been linked to an increased risk of certain cancers and potential reproductive problems. Heavy metals like arsenic and mercury are also targeted by filtration systems because they can cause long-term organ damage.
Microbial cysts, such as Cryptosporidium and Giardia, are microscopic parasites that can survive standard chlorination and cause acute gastrointestinal illness. These cysts are often mechanically strained out by home filtration devices, providing protection against waterborne pathogens. Filtration offers a layer of defense that helps reduce the body’s overall toxic burden.
Common Water Filtration Technologies
Consumers have several common filtration technologies available, each relying on a different mechanism to purify water.
Activated Carbon Filtration
Activated carbon filtration is the most widely used household method, where water passes through a bed of highly porous carbon material. This material uses adsorption, attracting and trapping contaminants like chlorine, volatile organic compounds (VOCs), and substances that cause unpleasant tastes and odors.
Reverse Osmosis (RO)
Reverse Osmosis (RO) is a purification technique that forces water through a semi-permeable membrane under pressure. This membrane blocks almost all dissolved inorganic solids, including heavy metals, nitrates, and salts, often achieving a contaminant removal rate of over 95%. RO systems are highly effective at producing pure water, though they typically require multiple pre- and post-filtration stages.
Distillation
Distillation involves heating water until it turns into steam, leaving behind virtually all non-volatile contaminants and minerals. The steam is then collected and cooled back into purified liquid water. This process successfully removes dissolved solids and kills microorganisms, but certain volatile organic compounds may vaporize with the water and require a secondary carbon filter for complete removal.
Addressing the Loss of Beneficial Minerals
A common concern with aggressive purification methods like Reverse Osmosis and Distillation is the removal of naturally occurring beneficial minerals. These systems strip out dissolved solids, including minerals like calcium and magnesium, which contribute to water hardness. Water that lacks these minerals can taste “flat” to some drinkers, leading to questions about nutritional impact.
Calcium and magnesium in drinking water offer health benefits, including support for bone and cardiovascular health, and are easily absorbed by the body. However, for most people with a balanced diet, the majority of their daily mineral requirements are met through food, not water. This means that their loss through filtration is not typically considered a serious nutritional risk.
For those who prefer the taste or want to restore the mineral content, remineralization options are readily available. Many modern RO systems include a post-filter cartridge that reintroduces small amounts of minerals like calcium and magnesium to the purified water. Other options include using concentrated mineral drops added manually, which helps restore a more natural and palatable flavor profile.