Do shower filters actually work?

They can, but it depends on five things:

1. What kind of filtration media is in the shower filter (KDF vs. carbon vs. calcium sulfite, a blend, or something else) and if it’s capable of removing the contaminants in your water.

2. How much of the filtration media is present— a teaspoon of KDF will do a lot less filtering than a cup of KDF!

3. How long the media lasts— a filter may be able to remove 99.9% of chlorine for a very short period of time— but it’s more important to know how effective it still is at 90 days. For example, Aquasana’s filter is verfied to remove 90% of chlorine for 10,000 gallons (about 588 showers), whereas Crystal Quest is only verified to remove 72-89% of chlorine for up to 500 gallons (29 showers).

4. What your definition of “works” is: a filter that softens your skin and hair is very different than a filter that removes chlorine for asthma, or PFAS and microplastics for general health.

5. How much of a given contaminant is in your water (you can check what is in your city’s water supply on the EWG database, here.)

Why is NSF certification important for shower filters?

Because it means the filter is actually able to do what it says. It means a third party laboratory has tested the claims made by the shower filter brand and verifies that they are true. It also means that there is enough filtration media, that it is set up correctly inside of the filter, and that it will be effective for a certain number of showers or gallons of water. For companies without NSF certification, or internal testing, I’m not sure how they actually know what it can remove. For companies that don’t share their internal testing data (“proprietary”) I imagine it’s because it shows a sub-par performance. Otherwise they’d post it and brag about it!

What can shower filters remove?

Most shower filters remove chlorine, and not necessarily much else. Chlorine is used to disinfect the water supply and ensure your water doesn’t have bacteria, viruses, or fungal growth in it. The only shower filter I know that is verified to remove more than just chlorine is listed above, the Weddell Duo, that can also remove PFAS and particulates (microplastics). The Watersticks’ Shower Stick can remove calcium and magnesium, and though it doesn’t have NSF testing for the entire unit, the filtration media inside is certified.

Why remove chlorine from shower water?

Chlorine can affect your health in two ways: coming into direct contact with your skin, and being inhaled into your lungs as a vapor from shower steam. With direct contact, chlorine can cause itchy skin and dry hair. Inhaling it is associated with lung and throat irritation, typically at the higher doses found in swimming pools, but sensitive individuals may notice it in a shower, depending on your water supply. Your skin does not absorb chlorine into the body very well, so this is less concerning.

I have lead pipes. What shower filter removes lead?

None do, to my knowledge, and that’s probably OK. That’s because lead, bad as it is, doesn’t get into the body through water absorption by the skin. It also isn’t aerosolized into shower steam, meaning you won’t breathe it in. The main way lead gets into the body is by drinking it, which is why it’s important to use a water filter for your drinking water. So, be careful not to drink shower water if you have lead pipes. If you are still concerned, you can install a whole-house water filtration system that is certified to remove lead, have lead pipe remediation done, or keep your eye on the market for a shower filter that is NSF 53 certified to remove lead (again, none are to my knowledge, probably because it’s not a primary concern for exposure).

What is NSF 372 certified?

This doesn’t mean the filter has been tested to remove lead. It just means the filter itself does not contain lead.

Are shower filters good for hair?

Yes! Shower filters target chlorine removal, and since too much chlorine can lead to dry, frizzy hair, a shower filter can help.

What is NSF 177 certified?

NSF/ANSI 177 certification is specific for shower filters, and means that a shower filter can remove at least 50% of chlorine from the water. Some shower filters are certified to remove 80-90% for many, many gallons (like 10,000), some are able to remove 50-90% for 25,000 gallons, etcetera— but most shower filters are still not certified at all.

What is NSF 42 certified?

This certification covers lots of different things, all having to do with “water aesthetics”— basically, the impurities in water that make it look, or smell, unappealing. This includes chlorine (smell) and particulates like iron that make the water look rusty, among other contaminants. Importantly, if a filter is NSF 42 certified, it doesn’t mean it’s certified to remove every single impurity on the NSF 42 list. A filter can be NSF 42 certified to just remove iron, or just for chlorine, etcetera. You should definitely look at the list of testing to see exactly which of the NSF 42 impurities were tested for and removed effectively. This is used more often for tap water drinking systems, and less often for shower filters, because these two types of filters are held to such different standards and work so differently.

What is NSF 53 certified?

This certification covers lots of different things, all having to do with health issues— so, impurities like PFAS, lead, chromium, and others. Importantly, if a filter is NSF 53 certified, it doesn’t mean it’s certified to remove every single impurity on the NSF 53 list. A filter can be NSF 53 certified to just remove PFAS effectively, but not remove lead, for example. You should definitely look at the list of testing to see exactly which of the NSF 53 impurities were tested for and removed effectively. This is used more often for tap water drinking systems, and less often for shower filters, because these two types of filters are held to such different standards and work so differently.

What is the best shower filter for hard water?

The Watersticks brand, listed above, has the Showerstick, which is an ion exchange filter that can capture Magnesium and Calcium, the minerals that make water “hard.” Magnesium and calcium in shower water is not harmful, but can dry out your hair and cause a residue to build up in it. The vast majority of shower filters can capture some of these minerals, but since they are small, and usually use KDF, they don’t do this nearly as efficiently, and you would need to change the filter very often. An inline stick filter like this can be a more convenient option than a whole-house water softener, if you are primarily concerned with hard water’s effect on your skin and hair.

Can shower filters remove heavy metals?

Maybe a tiny bit, but shower filters cannot remove a meaningful amount of heavy metals from the water supply.

Here’s why: if you have Arsenic in your water supply (as Portland, Maine does), and you’d like to remove it, a shower filter with activated carbon in it that advertises that it can remove Arsenic may sound nice— but, it may only remove say, 1 molecule of Arsenic, once, in the first week. A larger activated carbon block that filters cold water moving through it at a moderate kitchen tap water rate can remove more, if pH conditions are right and other contaminants aren’t inhibiting it. A shower filter will remove far less because of the relatively small size (meaning smaller amounts of carbon), the hot temperature of the water, and the great force and speed it’s pushed through at. There simply isn’t enough time for the media to capture contaminants, and heat changes the ability for contaminants to bind to it, as well. A whole-house Reverse Osmosis system would be the only way to meaningfully decrease shower water levels of Arsenic.

If you’re just trying to soften your skin, that’s OK. But if you’re tricked into thinking you’re reducing your Arsenic exposure levels, then that’s not fair.

This is why third party testing and certification is so important for shower filters. It confirms whether or not the filter actually works like it says it does.

Do you need to remove arsenic from your shower water?

Probably not. Drinking water with arsenic is the main way it get into your body. It is not able to pass through the skin, and while you can breathe it in from dust, your shower water would have to be 1,137°F for it to become aerosolized in shower steam. Prioritize removing arsenic from your drinking tap water instead. Some shower filter brands advertise they can remove arsenic, but this is likely just to make them appear more effective.

Can shower filters remove PFAS?

Yes, but only if they are tested and certified to be able to. The certification is NSF/ANSI 53, and you should also see results showing exactly how many PFAS were removed and for how long. Here is an example.

Can you absorb PFAS through your skin?

Unfortunately, yes.

What are disinfection byproducts (DBPs)?

Disinfectants like chlorine, or in some cities, chloramine, are added to water to prevent contamination. This is a good and very important thing to protect us from a water supply that spreads typhoid, dysentery, or other bacterial, viral, or fungal diseases. However, a bad side effect is that chlorine and chloramine react with organic materials in the water and produce disinfection byproducts, or DBPs, that are much more dangerous to human health than chlorine itself. There are many types of DBPs, including chloroform, trihalomethanes (THMs), haloacetic acids (HAAs) and others.

Can shower filters remove disinfection byproducts (DBPs)?

Maybe. Theoretically, an activated carbon filter could remove DBPs, but there are no shower filters with this certification yet. For regular drinking water, you would look for NSF 53 certification that specifically is shown to remove them, but for shower filters, this just doesn’t exist yet. The only way to completely remove them from shower water would be to install a whole-house Reverse Osmosis system. Ideally, water treatment plants will move toward using ozone or other effective alternatives in the near future.

Why are there so many misleading shower filter claims?

There is SO much healthwashing in the shower filter business! My best guess as to why is three-fold:

1. Water contaminants are invisible, and often don’t have a detectable smell or have a color, so it’s very easy to claim more purification is happening when it’s really not. Self-testing your water is the best way to know if a filter is working, but it can be really expensive —running you hundreds of dollars to assess both before-and-after samples for heavy metals, PFAS, and other issues. Therefore, a company can get away with exaggerated claims. This is the most sinister of my guesses; that there is some level of deception happening for the purpose of making money.

2. Some brands may take legit, general facts about filtration media and retroactively (but inaccurately) apply them to their product specifically. Similar to the Arsenic example above, a good amount of KDF can remove heavy metals from water— there’s research on this. But if you put a teaspoon of KDF into a shower filter and run hot water on high pressure through it, it may not remove any! It’s context-dependent. So, I think some claims are made about the media filtration generally, but aren’t actually tested or verified for the shower filter itself.

3. Competition! If your shower filter’s “contaminants removed” list is shorter than your competition’s, it might look less effective to the untrained eye. If one brand is claiming it can remove a long list, then it perpetuates the spread of unverified long lists across brands.

How can I tell if my shower filter is working?

There are three main ways:

1. Trust high-quality third-party lab testing companies: a filter both tested and certified by NSF, IAPMO, or WQA will work for the contaminants listed, for the amount of time it’s verified to be effective for.

2. You can test the water yourself with a before and after sample (water tests I recommend here). It can get expensive, but is the most direct way of knowing.

3. You can trust how your hair and skin feel and look. This likely means the filter is effectively reducing chlorine. It may not be removing other contaminants, which is just fine if that’s not what your goal is.