The Best Showerhead Water Filters

We solicited independent lab data from the makers, where it existed. We also used digital and chemical tests designed for pools and aquariums and avoided painfully unreliable home test strips. The upshot is that you probably shouldn’t expect these shower filters to soften the mineral hardness of your water or remove most substances.

So what do these showerhead filters actually do, in a way we can measure? They filter chlorine and chlorine compounds, mostly through chemical reactions. Pretty much every American city adds low concentrations of chlorine or chlorine compounds to drinking water to kill potentially harmful bacteria. This is all well and good when the water’s still in the pipes. But chlorine’s not exactly great for your hair or your skin, and few people like to drink it. Some are also especially sensitive to the taste or smell, or prone to skin reactions.

That’s where home filters come in. The most prominent shower filters rely in part on a zinc-copper mixture called KDF-55, known to be quite effective at neutralizing pure or “free” chlorine. Other common substances used to treat chlorine and chlorine compounds include calcium sulfite and activated carbon. The most effective filters use these in some combination.

The market for filtered showerheads remains young and largely unregulated, and performance claims are only rarely backed up publicly by independent data. We made lots of requests, but few shower filter companies hand over their lab results. (Thank you, Aquasana, for being an exception.)

Some makers told us that independent labs and certifying bodies have been backed up, and that data is forthcoming. Many offered customer satisfaction surveys instead. This all means that some skepticism is warranted.

After all, a filter must be relatively small to fit into a showerhead. And yet it’s being asked to filter gallons of water each minute, pushed out at both high temperature and high pressure. A showerhead filter poses a daunting engineering challenge, as compared to countertop water filters that treat only a small amount of water at a time—or a bulky reverse-osmosis device that can plug into your under-sink plumbing.

We’ve seen little evidence that the most common types of showerhead filters have much effect on the softness or hardness of water, or on calcium buildup. In fact, some early academic studies present evidence that they don’t. The shower filters we tested also had very little effect on the sum total of dissolved solids in our water, according to measurements with a TDS meter—i.e., the filters aren’t removing a large amount of materials or minerals from the water.

I wasn't able to test claims by some companies that these filters remove heavy metals like lead and arsenic, which thankfully aren’t in my pipes. But if you believe you have dangerous lead or arsenic in your water, you probably shouldn’t try to fix the problem with a mail-order showerhead. Talk to a water treatment professional or your public health authority.

If you live in a major US city, chlorine is likely not what your city uses to treat the water in its pipes. New York, Chicago, Seattle, and Phoenix use chlorine, sure. But Los Angeles, Philadelphia, Atlanta, Boston, and most big cities in Texas don’t.

More than half of American big cities use a substance called chloramine, a more stable and enduring chemical that’s harder to filter and test. To test, I got out my handy digital water colorimeter and a somewhat nasty chemical indicator, and then tested the ability of each shower filter to treat chlorine compounds in the water.

First I tested the total chlorine in the water without any filtering, then I tested the water filtered by the showerhead. I did each test multiple times to account for imprecision or fluctuations in municipal chlorine levels. In most cases, I did this over multiple days. (One showerhead’s filter broke from its own weight on the second day of testing. I felt comfortable not recommending this showerhead, despite only one day of middling test results.) As we update this guide, we’ll continue to test the most effective showerhead filters to see how their efficacy changes over time—and add any new shower filters we’re able to recommend.