According to the marketing pitches, filters make for tastier, safer, healthier water. Which… sounds like it should make sense? Your anal-retentive roommate who keeps going on about his jug of filtered water certainly believes it, too.
But is filtered water actually safer and healthier than the good ol’ tap?
First off, let’s look at what these filters do. In a nutshell, they run water through various substances (activated charcoal, for example, which absorbs toxins, or activated carbon and ion exchange resins, which attract and adsorb — not absorb! — particles) that pluck unwanted chemicals out of the water, including metals and chlorine residues. Unlike municipal water, though, personal filters aren’t subject to any government oversight or regulation — although the independent, nonprofit NSF International provides certification and standards for many filters on the market.
But does this removal of chemicals, y’know, help you in any way? That all depends on what’s in your tap water to begin with. Some water filter models are able to deal with certain toxins, like lead, that can come from outdated pipes. But as Raymond Letterman, professor emeritus of civil engineering at Syracuse University and an expert on large-scale water treatment systems, told The Daily Beast in 2014, “You might want a more serious intervention than store-bought filters if your pipes are actually leaching lead.”
Efficacy aside, some filters can actually add bacteria to your water. Because bacteria grows best in dark, moist places, water filter manufacturers do put small amounts of bactericide in their products to lessen the chances of infestation, but it doesn’t always work, according to Letterman. “Unless you have a chemical disinfectant in the water, like chlorine, you’ll always get some bacterial growth on filter surfaces. It’s just inevitable,” he explained.
One German study of such bactericide-impregnated filters, in fact, found that filtered water usually contained more bacteria than tap water. And in some cases, bacteria colony counts in the filtered water were 10,000 times more than those in regular tap water. Many of the bacteria were harmful to humans. After reviewing the results of the study, the researchers went so far as to recommended that people with weak immune systems boil their filtered water (after it had been filtered!) to lessen their risk of infection. In the 1990s, the Canadian government even briefly considered banning such filters until further research on bacterial growth had taken place.
All in all, it sounds like filters hurt more than they help, so what’s the case for the defense? There doesn’t seem to be much more to it than the idea that by using a filter, you save on the waste from all those plastic water bottles that you might use otherwise. And that’s about it: Filtered water versus bottled water. Because there couldn’t be an eco-friendly alternative, like that EPA-regulated stuff that comes right from your tap, could there?
In short, if you have a roommate who’s always on you to replace the filter, maybe consider replacing your roommate instead.