Is Filtered Water Healthier Than Tap? There’s One Crucial Overlooked Factor

Adulthood can comprise tiny, routine joys, like replacing the carbon filter in your water pitcher at precisely the right time. In fact, if you’re giddy at the idea of having a filtered pitcher, that’s a sure sign of growing older, and you are not alone. In 2022, the market for activated carbon filters was valued at $543 million, and is projected to swell to $4 billion by 2035.

Ideally our tap water is clean and safe to drink by the time we turn on the faucet. These filters, for the most part, improve our tap water’s appearance and taste. So if there any value at all in an additional filter? Do these filters at all improve our health?

How do water filters work?

Most at-home water filters, like the Brita and its competitors, use carbon to help filter the water. Carbon filters halt particles with adsorption, in which a solid creates a thin film from a gas or liquid. The solid granular activated carbon attracts various molecules, reducing their presence in tap water that passes through.

Commercial carbon filters recommend changing or cleaning every two months or 40 gallons because they have a fixed capacity. After a certain point, the thin film saturates the filtering surface. Without cleaning, bacteria can start to build up and even add unwanted compounds back to your water, Yoram Cohen, a chemical and biomolecular engineering professor at the University of California, Los Angeles’ Institute of the Environment and Sustainability, tells Inverse.

What they don’t do is purify untreated water. “I would not recommend [carbon filters] as the ultimate safeguard,” Cohen says. “Because people at home don't have monitoring devices” to test how clean their water actually is post-filter.

In addition to chlorine, carbon filters can remove volatile organic compounds (VOCs) and, depending on the model, other contaminants such as per- and polyfluoroalkyl substances (PFAS), a.k.a. forever chemicals. VOCs, depending on where you live, may include the contaminants benzene, toluene, and methyl tertiary butyl ether (MTBE). Batterman says that basic carbon filters aren’t certified to remove PFAS, so you’d have to look for more sophisticated models for that job.

Is carbon-filtered water better than tap?

That depends on what you mean by better. “The greatest use of the carbon filter is in adsorbing any excess chlorine that may be in the water,” Cohen tells Inverse. “The carbon filter basically improves the taste significantly.”

It usually improves taste, but it’s not necessarily any healthier. In fact, Cohen says he doesn’t know of studies that assess health differences between those drinking filtered and unfiltered tap water.

What’s in your tap water depends on where you live. If you’re hooked up to a municipal water supply, your town or city takes care of thoroughly treating your water at its source.

It may still contain lead, arsenic, and mercury at extremely low, federally allowed limits. (To be sure of what you are drinking, you can test your tap water to get to know exactly what’s in it.)

Your tap water may also contain some chlorine or chloramine as a residual disinfectant. Water pipes can develop biofilm, or a sludgy internal coating that can harbor bacteria, says Stuart Batterman, an environmental health and engineering professor at the University of Michigan’s School of Public Health. As clean water streams through plumbing, it may pick up some of this biofilm. And that’s where a carbon filter may come in handy.

So while using a carbon filter may not be adding years to your life, it’s performing a service, even if that just means giving you better tasting water. If you relish replacing your filter every two months, may you happily replace many filters.