Is Your Water Filter Doing More Harm Than Good? Here’s How To Safeguard Your Drinking Water

My hotel room was conveniently outfitted with a water filtration tap for filtered water on demand. I thought, great! But after quickly chugging a glass, I immediately noticed that the water smelled and tasted overwhelmingly algal and swamp-like—like what you’d equate with a fish tank. Coincidentally, I began experiencing acute gastrointestinal symptoms in the weeks that followed, with tests eventually confirming a diagnosis of an intestinal parasitic infection.

Was the filtered water the culprit? There’s no way of knowing for sure, but it certainly stands out as a red flag, and science says it’s possible. The experience compelled me to take a closer look at water filters—when they can help us, and when they can fall short and harm us.

Water filtration devices are increasingly being used as a countermeasure to deal with tap water quality concerns by removing unwanted chemicals, tastes, and odors from the public water supply. While they can contribute to increased water safety and an enhancement of water quality, if they’re not adequately maintained, they could actually be doing more harm than good.

How well do water filters actually clean water?

Most point-of-use filtration systems use granular activated carbon, designed to transform what comes out of your tap into higher-quality and better-tasting water. These filters are primarily used to remove non-biological contaminants based on the certifications they hold. Certification of water quality through NSF/ANSI Standards 53 and 42 targets the removal of things like heavy metals, fluoride, and a range of volatile organic chemicals, as well as aesthetic contaminants such as chlorine (for taste and odor concerns), chloramine, iron, and zinc.

What they don’t remove is bacteria. “You cannot assume that if the filter removes chemicals, it will also remove germs,” stresses Samantha Nazareth, MD, board-certified gastroenterologist.

It’s important not to mistake filtration for purification. Brita makes it clear that their filters are not intended to purify water, and filter manufacturers include in their documentation that they shouldn’t be used with water that is microbiologically unsafe—though most consumers won’t know if this is the case.

Can an old water filter make you sick?

“People can get sick from filters that are poorly maintained,” says Nancy G. Love, PhD, distinguished professor and award-winning environmental engineering researcher at the University of Michigan. According to Love, studies show that bacteria grow well on activated carbon (including point-of-use filters), and that filters can actually elevate the levels of bacteria in our drinking water.

We know that safe levels of chlorine are added to drinking water to provide protection against waterborne disease outbreaks, but according to Justin Wang, CEO of LARQ, a brand of innovative hydration products, by removing chlorine, filters become the perfect breeding ground for bacteria, and the source of contamination.

A study that tested the microbiological quality of filtered water in a household water filter system found that, in some cases, bacterial colony counts in the filtered water were 10,000 times those in tap water, suggesting growth or biofilm formation in the filter material. Equally alarming is research showing how dramatically the bacterial composition changes across a filter, which in turn may influence our gut microbiome.

In some cases, bacterial colony counts in filtered water were 10,000 times those in tap water.

“While the vast majority of bacteria in drinking water are harmless (just like the bacteria in the food we eat),” notes Love, “if a pathogen was present, studies have shown that certain pathogens might be retained and grow on the filters.”

Findings from a recent study demonstrate that filters may increase one’s exposure to opportunistic pathogens that are otherwise present at lower numbers in distributed drinking water. “A drinking water that is well-maintained would not have these problems,” says Love, “but a large building with loss of chlorine residual in the upper floors or old piping that is not well-maintained (like, possibly, a hotel room) could have a problem.”

Water filters are only as good as their upkeep

Because most filters work by capturing and holding contaminants, it’s important to replace them regularly to avoid them becoming incubators of bacteria. “Water filter components absorb a finite amount,” says Wang. “Once that threshold is reached, the water can still be cycled through, but it will not remove any contaminants and may actually reverse contaminate the water with the bacteria growing in the filter.”

Brita’s guidelines suggest that their standard pitcher filters expire after 151 liters, whereas LARQ designed its advanced filter to last for 227 liters of water before needing replacing.

“Filter usage is notoriously difficult to track, and many consumers do not replace filters in a timely manner,” says Wang. “Most traditional filters offer a generic replacement recommendation, often including a timed light or reminder sticker for your calendar to remind you when to replace your filter.” LARQ’s pitcher does the monitoring for you by tracking household water consumption with a built-in sensor that conveniently connects to an app.

Water filters aren’t a silver bullet

It would be unfair to expect filtration to magically make all water completely safe, particularly when the liquid we’re filtering is coming from an aging infrastructure.

“Water filtration is a very effective method when done as designed, but it will struggle if one has to filter water that comes from a treatment and/or distribution system that is in disrepair and has had inadequate investment,” says Love. Much of the water distribution system infrastructure in the U.S. is aging and deteriorating, with cities such as Philadelphia still relying on pipes that were put in the ground before the Civil War. Water utilities in the U.S. and Canada are only replacing pipes every 125 years on average, well beyond the recommended timeline for many pipe materials.

Deteriorating drinking water systems are vulnerable to a host of problems, affecting the ability to provide safe water. By the time water reaches your sink, it can be contaminated with the accumulated build-up (rust, metals, algae, biofilm, bacteria, viruses, parasites, etc.). According to Dr. Nazareth, a number of bugs known to cause lung, blood, skin, and brain infections have been found in biofilm from pipeline sources.

With pipes tucked away underground, Love highlights the difficulties in convincing people an “invisible” water infrastructure needs investment when they can’t see it, and notes that this under-investment is costing us now.

A multi-barrier approach is best

No one technology does it all. “The gold standard of drinking water is the use of a multiple barrier approach, where we use multiple unit technologies to address different contaminants,” says Love.

If your tap comes from an old water distribution system—one known to have problems, or if there are frequent repair issues—Love suggests that a relatively low-cost option for drinking water is to use an activated carbon block filter and then also boil the water to disinfect it. Unlike its granular carbon counterpart, carbon block—a solid block of compressed carbon—is very effective in filtering out large quantities and a variety of contaminants, thanks to its larger surface area.

Following the 2014 Flint, Michigan, water crisis, in which city drinking water was contaminated with lead, and because the plumbing is very old, hydration stations in Flint schools now employ a multi-barrier approach, according to Love. Water goes through an activated carbon block filter, followed by a membrane, and then an LED UV lamp for three layers of protection.

For a multi-barrier approach at home, the LARQ Pitcher uses a two-step filtration and purification process using its PureVis UV-C LED light to eliminate bio-contaminants. In lab testing, a three-minute cycle of UV-C light eliminated upwards of 99 percent of E.coli and salmonella.

Best practices when using a water filter

1. Flush before every use

“I am actually wary of filtered water that is not used routinely,” says Love. “I trust filtered water if I know the status of the filter, and still I always flush the filter (by letting the water run) for a few seconds if it has not been used regularly.”

When using hydration stations in public spaces (think airports), look for an indicator light. If it is anything other than green, Love recommends not using it. Always flush for a few seconds before filling your bottle to move any biofilm that may have accumulated.

2. If possible, avoid tap water if you’re immune compromised

For people who are immune compromised or if one is making baby formula, Love advises against drinking tap water or using activated carbon filtered water, and instead favors reverse osmosis water or purified bottled water as better options.

3. Use filters when traveling abroad

“Most contaminated water infections I see come from those traveling abroad,” says Dr. Nazareth, calling attention to the challenges of consuming water of unknown quality. Stick to bottled water, or bring along a bottle like LARQ’s that’s outfitted with UV-C light technology in the bottle cap, and another with a filter for multi-barrier protection.

4. If the water tastes bad, it probably is

“Our sense of smell and taste are our first line of defense,” says Dr. Nazareth. “Our taste buds and nose are very sensitive to foul-tasting things in order to protect us.” So, if something tastes off, it probably is.

Water filtered with a maintained unit should not smell or taste foul, according to Love. However, “If water has a natural smell, that may be geosmin or methylisoborneal,” she says. “These are natural organic compounds present in natural waters that are highly odorous (they smell musty) but not harmful.” Certain parts of the country can have these chemicals in their treated drinking water, and while present at very low levels so that you can’t smell them, they can accumulate in a filter to a level that can be detected by the human nose. “Otherwise, I would not use filtered water that has any features to it that are unpleasant,” says Love.