Water filters purify your water of all contaminants, right? Maybe not. So what are all the commercial water filters for, the ones that claim to “purify” your water so it’s “crystal clear”?

Water you might think is contaminant-free might actually still contain harmful residuals like lead, mercury and asbestos. No amount of lead in water is a safe amount to ingest, according to the Environmental Protection Agency (EPA). When purchasing a water filtration system, make sure to check that the label clearly advertises lead filtration or reduction.

How It Works:

Most filtration systems work by having the water pass through carbon blocks — similar in appearance to large black stones — that absorb and break down particles as they pass over the surface. Others use mesh screens that trap particulate matter. Filters should be replaced every 120 gallons or every six months, and most filter replacements are also available for purchase in chain grocery stores. Newly purchased filters should be rinsed under water for at least 15 seconds before use to help wash out loose carbon particles that could inadvertently contaminate water.

Water filters are different from water purifiers. A purifier can be used on untreated water or water known to be contaminated, while filters should be used on already treated water, like tap water. Potable water is already filtered through the process of chlorination, which adds safe levels of chlorine to drinking water to disinfect and kill bacterias. Filters can only improve water quality by 20 percent, so while they make water healthier they do not necessarily make it completely safe. Most filtration services simply reduce chlorine taste and odor, which is the residual chloramine particles that remain in the water.

From filtered water bottles to refilling stations, which water filtration systems remove lead?

Filters in the Fridge:

It’s the quick-fix and cost-effective solution to at-home water filtration: the beloved Brita pitcher. Pitchers are meant to fill, filtrate and fit in the fridge. They filter by running tap water into a basin, then drip the water into a second basin of the pitcher. Most pitchers are available at supermarkets or home goods stores and range from $20 to $40.  

While the standard Brita pitcher does not filter for lead, their Longlast filters do through added absorbents integrated in the filters. The Longlast replacement filters last for six months but also cost roughly $10 more than the standard option. In comparison, the PUR ultimate pitcher includes lead reduction filtration systems that remove lead, mercury and pesticides but need replacing every two months.

At-Home Filters:

At home filters can be attached to the end of the sink faucet to directly filter water as it comes from the tap (and leave you with more fridge space). Most use a larger cartridge feature that allows for a three-level filtration process: first a mesh layer for large sediment removal, then an active carbon block for smaller contaminants and finally a chemical removal to filter out heavy metal contaminants like lead, mercury and nitrates.

At-home filters, such as those made by Brita and PUR, can be purchased for reasonable prices — $20 to $40 — at department stores. Most screw onto the end of the faucet cap and contain an indicator light of when it is time to change the filter, which is roughly every three months.

On-The-Go Filtration:

There are also water bottles for sale at supermarkets that tout on-the-go filtration. Yet, most of these filters only reduce the amount of chlorine and small particles in water. This does not necessarily filter harmful contaminants but rather improves taste. Filtered water bottles can run anywhere from $17 to $40 depending on the lifespan of the filter and make of the bottle.

Some travel bottles like LifeStraw Go Advanced water bottle are specifically designed to filter bacteria and parasites from water sources when hiking or camping. Some bottles tout adding fluoride elements to drinking water, and the $30 nkd POD advertises filters with a coconut carbon layer to improve taste. Brita water bottles — both the soft plastic sports bottles and hard plastic everyday bottles — do not filter for water and can leave mold residue stuck in the straw and mouthpiece if not cleaned properly.

School Water Safety:

If you’ve ever grabbed a drink of water from the water fountains on DePaul’s campus, you’ve probably seen the water bottle refilling station on the side of the wall. These stations — whose official title is the ezH2O bottle fillers — are made by the sink manufacturing company Elkay, whose headquarters are located in Oak Brook, Illinois. The stations use a polypropylene (thermoplastic) prefilter along with the standard carbon filter to remove lead and chlorine. The changing color system indicates the level of filtration — green is good, yellow means to replace the filter soon and red is time to change the filter. As long as the station is displaying a green light, your water is being filtered for lead. You can still drink water from a refilling station with a red light; the water just has less of a chance of being filtered through the additional system.