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Healthier Hydration: Why You Need to Filter Your Tap Water

Why and How to Choose a Water Filter for Better Quality Water

Key Takeaways:
  • The public water supply can sometimes contain higher than optimal levels of pollutants, and occasionally breach legal safety standards.
  • Filtering your water can remove the contaminants you are concerned about and benefit your gut health.
  • You can find out what is contained in the water in your area by consulting public records, or (for more detail) by paying for an analysis of the water in your home. 
  • It may be more practical to just invest in a water filter for preventative measures — especially given there are regular fluctuations in contaminant levels.
  • You can choose a filtration method, such as ion exchange or an activated carbon filter dependent on the specifics of what you want to remove.
  • Reverse osmosis is the most comprehensive filtration method, but in many cases, activated carbon filters are perfectly adequate.
  • A point-of-use filter (e.g. a jug) removes contaminants just from the water you want to consume.
  • A point-of-entry filter (installed near your home’s main water supply) treats all the water that reaches your home.

If you live in the United States or in pretty much any other developed country in the world, you can be thankful that the quality of the drinking water is generally good.

But while you can confidently drink from the water supply without getting a nasty water-borne illness, there can still be issues with the quality of water reaching our homes. 

In a 2020 podcast with Dr. Tina Beaudoin, I was surprised to learn there are far more reasons why you need to filter your tap water than you’d think. The list of potential pollutants in our water is very long, and apparently, it’s quite common for contaminants to breach official limits. 

If you are drinking several glasses of water a day (as we should all be doing to stay hydrated), filtering your water is something I advise you strongly consider.

Filtering might be particularly useful if you have an impaired immune system, thyroid disease, or gut issues/sensitivities. In this article, I’ll guide you through choosing a filtering system for your needs.

While we obviously want to limit excess intake of chemicals and toxins, especially when it comes to something as frequently consumed as water, it’s also worth remembering that ALL substances are made of chemicals. That includes the air we breathe, the food we eat, the fabric of our clothes, and our very cells. 

So we’re not trying to get rid of all chemicals — just the ones that might be bad for us if we get too much.

Water Quality Basics

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According to the U.S. Environmental Protection Agency (EPA), 90% of Americans get their water from about 150,000 public water systems, all of which are regulated by the Safe Drinking Water Act. About 10% of people get their water from private wells, which are not regulated [1]. 

Contaminants That Are Regulated

In total, the EPA regulates 90 individual contaminants in the public water supply [2]

The water contaminants that are regulated come under six different headings — here’s what these categories are, and some of the health issues they can cause [3]:

Contaminant TypeAdverse Effects on Human Health
Microorganisms (bacteria, parasites, and viruses related to human and animal feces)Can cause digestive illness.
Disinfectants (e.g. the chlorine added to water to kill microbes)Can cause eye and nose irritation, stomach discomfort, and anemia. May impair the developing nervous system in  babies and small children.
Byproducts of disinfectantsMay damage the liver, kidneys, circulatory system, and the developing nervous system. Also raise the risk of cancer.
Inorganic chemicals, such as arsenic, fluoride, and leadIn excess, can cause a wide range of health problems affecting the liver, kidneys, thyroid gland, nervous system, digestive tract, bones, skin, circulatory system, blood pressure, blood sugar, and cholesterol.
Organic chemicals, including volatile organic compounds (VOCs) and synthetic organic compounds (SOCs) Can damage the kidneys, liver, and nervous system; SOCs can also damage reproductive health.
Radionuclides (like radon, radium, strontium)Can increase the risk of cancer. 

Contaminants Not Regulated

While ninety might sound like a lot of chemicals to be checking for in water, it’s a less reassuring figure set against the 40,000 to 60,000 chemicals used commercially, (6000 of these account for more than 99% of the total volume of chemicals used globally) [4]. 

In 2017, the chemical industry was the second-largest manufacturing industry in the world, with chemical sales projected to double by 2030. Some of these chemicals will inevitably end up in our water supply [5].

Legal Limits Versus Healthy Limits

When weighing up if or why you need to filter your tap water, you also need to take into account that the legal limits for contaminants, may be quite different from the healthy level.

The EWG (Environmental Working Group), has defined upper recommended levels of contaminants in water that are much lower than those that are legally allowed according to the Safe Drinking Water Act.

If a city’s water supplies lie above these healthy limits (which they can do so for years) there are no legal repercussions, but there can be health-related ones.

If you know your city has contaminants above optimal levels, using a filter is definitely a good idea. If you have a health condition, I’d recommend it, even if your area has high water standards, to account for contaminants that may not be tested.

The bottom line is that filtering your drinking water is one area where erring on the side of caution is your best option. Some examples of the discrepancy between the official legal limits and the EWG’s recommendation are shown below [6]:

ContaminantClassificationFederal Legal Limit (Parts per Billion or Parts per Million)EWG Recommended Limit
AtrazineSynthetic organic compound (herbicide)3 ppb0.1 ppb
BariumInorganic chemical (comes from drilling waste, metal refineries, and natural erosion of rocks)2 ppm0.7ppm
GlyphosateSynthetic organic compound (pesticide)700 ppb5 ppb
NitrateInorganic chemical (comes from fertilizers, septic tank leaks, sewage, and erosion of rocks)10 ppm0.14 ppm
PFAS (Per- and Polyfluoroalkyl SubstancesSynthetic organic compound (used in manufacturing consumer and industrial products)No standard0.01 ppb
TrihalomethanesDisinfection byproduct80 ppb0.15 ppb

Water Pollutants Can Alter Your Microbiome

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Except for chlorine disinfectants, which help destroy harmful microorganisms and therefore protect the gut from infection-related dysbiosis [7, 8], all the other categories of contaminants can contribute to imbalances in the gut. 

For example:

  • Pathogenic microorganisms /parasites, e.g. Cryptosporidium, Giardia, andEscherichia coli (more likely in well water) can:
    • Trigger gut inflammation and increase intestinal permeability (aka leaky gut) [9]. 
    • Infect the intestine and destroy microvilli (absorption surfaces) in the gut [10].
    • Reduce the number of beneficial bacteria and increase the number of bad guys, increasing the body’s vulnerability to other pathogens [11].
  • Inorganic contaminants: include mercury, nitrate, barium, cadmium, copper, lead, and arsenic. They can alter the composition of the gut microbiome, which can stop microbial genes from expressing and functioning properly. Downstream effects may include problems with our metabolism, immune system, and neurological function [12].
  • Organic contaminants: include human-made chemicals from things like lacquers, paint strippers, waxes, cosmetics, cleaning supplies, and pesticides. In lab studies they have been shown to inhibit the metabolic activity of good bacteria, significantly change their gene expression, and cause some species to metabolize fats differently [12, 13].
  • Radionuclides: have been linked to reduced microbial diversity and richness, more pathogenic bacteria, and fewer beneficial ones [14].

A healthy microbiome is not just important for digestive health, but can also impact things like mental health, keeping your thyroid healthy, and allergies. So it’s well worth taking the steps to make sure your water supply doesn’t damage your gut bacterial balance.

What About the Fluoride in Water? 

While fluoride at a level of 0.7mg per liter, is argued to benefit dental health [15], too much fluoride has been linked with thyroid issues.

You can find out whether your water has added fluoride, and how much, by checking the CDC website here.

Opinions differ as to whether excess fluoride in water is a credible concern. The published research that sheds the most light on the issue is a 2018 systematic review, which collected data from 24,864 participants. It found a positive correlation between too much fluoride and hypothyroidism but also found that the data was insufficient to confirm that high fluoride levels actually cause hypothyroidism [16].

While we don’t have too much research to answer the fluoride-in-water question one way or another, you may want to remove excess fluoride from water supplies that contain more than 0.7mg per liter. And if you have poor thyroid health and/or have had difficulty with managing your thyroid lab levels, it may be worthwhile to completely filter out the fluoride to see if it helps. 

Find Out the Quality of Your Water

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Before deciding on a water filtration system, you’ll first need to get a feel for the water contaminants you are dealing with in your own water supply.

To do this, visit the Environmental Working Group’s (EWG’s) Tap Water Database and key in your zip code to access a report of the water quality in your area. 

  • The report will detail the contaminants in your water supply that exceed both the legal limits and the health guidelines the EWG has set.

To double-check the EWG’s report, you can also contact your local water supplier and ask for the most recent annual water quality report. 

Some contaminants vary, depending on the specifics of your house and plumbing.

If you’d like a more accurate analysis of the water actually coming out of your own faucets you can pay for a test from a certified laboratory. For example, National Testing Laboratories, Ltd., has tests ranging from $179–$299. Some examples of why you may consider this is living in a house with older plumbing, or near areas of industrial mining or large-scale farming with heavy herbicide/pesticide use.

Once you know which specific contaminants you are dealing with, then you can decide which type of filter will be best for your situation [17].

Fortunately, the EWG website is very helpful here too — below the water report for your zip code, you’ll see a table that shows the types of water filters that can reduce the specific contaminants in your own water supply [17].

Types of Water Purification

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Let’s look at the commonest ways of methods of filtering water, which are [18]:

  • Reverse osmosis
  • Activated carbon
  • Ion exchange
  • Distillation

Bear in mind that at least two or more of these methods will often be combined in one system, which can either be: 

  • A point-of-use device, (e.g. a filter jug, or an under sink/countertop system that filters the water coming out of a specific faucet).
  • Point-of-entry device (centrally attached to filter all water coming into the house).

You don’t necessarily need to go in for more expensive point-of-entry systems — you can usually achieve good enough quality water with a cheaper point-of-use product. But, if you live in an area with extremely poor water quality, next to industrial sites or farmland, and/or have a chronic health condition that’s highly resistant to treatment, this type of system is consideration.

Reverse Osmosis

Reverse osmosis involves pushing water through a semipermeable membrane with such a small pore size ( 0.0001 microns) that only water molecules get through and all other components including bacteria, viruses, and parasites get left behind. 

This makes it the most effective kind of filter for removing the broadest range of contaminants (other than radon gas). The downside is that this technology is expensive (typically hundreds of dollars), can make water taste flat, and wastes 3 times as much water as it cleans.

It also removes minerals that you might actually want in your water, such as magnesium and calcium. To avoid trace mineral and electrolyte imbalances, it’s recommended you add some back into your water before drinking, if you choose to go with an RO system.

Activated Carbon

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Activated carbon (charcoal) filters come in two forms — carbon block and granulated carbon and work by having a huge surface area that adsorbs (traps) dissolved contaminants. Carbon blocks are usually more expensive than granular activated carbon but are generally more effective because they have more surface area that comes into contact with your water. 

The best activated carbon filters (block carbon) can reduce the levels of chlorine, asbestos, lead, mercury, and volatile organic compounds, or VOCs. They may also remove some radon.

However, activated carbon does not remove arsenic, fluoride, chromium, or nitrate, though some carbon filter brands also offer an arsenic- and fluoride-filtering attachment. The pore size of activated carbon is also too large to effectively filter out bacteria. So a carbon filter is only effective on water that is already safe to drink from a microbiological point of view (i.e. the public supply).

Ion Exchange

Ion exchangers for home use water treatment are more about softening hard water than actually filtering out contaminants. They replace calcium and magnesium, which build up as scale deposits, with sodium and/ or potassium and can also reduce barium and radium levels. 

Ion exchangers/water softeners that add sodium to your water may not be good for people following a low-salt diet. They definitely shouldn’t be relied upon for water filtration purposes.


Distillers are less common than other water cleaning devices in domestic situations and work by heating water to boiling and collecting water vapor to kill pathogens and most contaminants. However, they do not remove chlorine or volatile organic compounds.

Like reverse osmosis, this type of treatment can make water taste flat because minerals and dissolved oxygen are removed.

Choosing the Best Filter for Your Needs

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As I alluded to earlier, the filter system you choose depends on why you need to filter your tap water — i.e. what you are trying to remove.

However, the most effective type of filtration system is generally agreed to be reverse osmosis combined with a carbon filter [17, 18]. This might be good for those who have a compromised immune system or a serious chronic health condition, as this combination effectively filters out nearly all common contaminants. But because the reverse osmosis system is wasteful, the EWG suggests applying it only to the water you use for cooking and drinking [18]. 

In many situations, carbon filters, which are often combined with ion exchange in jug filters and under-sink systems, can be perfectly adequate. As a general rule, I’d say to start with a carbon filter, unless you have specific health needs or live in a particularly bad area for water (you can always move up to using a reverse osmosis filter if you need one).

Carbon filters are typically more affordable, remove plenty of contaminants, and may be all you need [17]. However, carbon filters should only be used with already disinfected water as they don’t filter out bacteria. Certain brands also provide an arsenic and fluoride filter attachment, making it a viable option for those with persistent thyroid concerns.


To check you are purchasing a water filtration system that is reputable, check it is certified by one of the following: 

Good Maintenance is Vital

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Once you have chosen the way you want to filter your water, the only thing left is to remember to maintain your system. This means regularly changing filter cartridges, to the schedule that the manufacturer recommends.

Because your filter cartridge is collecting potential contaminants over time, pollutants such as bacteria, pesticides, and lead, may build up in the filter and start passing back into the water if you do not replace it. 

With plumbed-in systems, clogged filters can also mean decreased water flow through your pipes.

However, as long as you know when and how to change your filter, and the correct filter to buy, you can carry on enjoying the benefits of filtered water without interruptions [19].

What About Well Water?

If your water comes from a well, the EPA recommends testing your water every year for nitrates and coliform bacteria and asking your local health department or local groundwater-based water system about contaminants of concern in your area [17]. Well water is much more likely than public water supplies to be contaminated with radon gas, so it’s also worth using a lab certified to measure this harmful gas (remember, RO doesn’t filter this one).

If you do have radon in your water supply, the most effective way to get rid of it is with an aeration system [20]. This system adds air to your water in a tank and then vents the air and radon outdoors, away from the house.

Well water can also contain bacteria, parasites, and viruses, so must be filtered through a small pore size that stops these from passing through (e.g. a reverse osmosis membrane), or else disinfected with ultraviolet light. Well water is, therefore, an exception for when you might jump straight to reverse osmosis and not try a carbon filter. You might also want a point-of-entry filter in this case.

Filter Your Tap Water for Peace of Mind

Water is so essential to our health that it’s worth taking the extra step to ensure any possibly harmful components get filtered out. Drinking filtered water will help protect your gut microbiome and immune system, and you’ll avoid unwittingly consuming unhealthy levels of contaminants if there’s a breach of safety standards in the public water supply.

In most scenarios, a point-of-use filter will be perfectly adequate (meaning you might shower and bathe in water that contains trace contaminants but don’t consume these in the water you drink and use in cooking). But the type of filtration you use will depend on the main pollutants in your water and the ones you particularly want to avoid.

If you need more help with health issues that may be related to water quality (for example, parasitic infections, microbiome disturbances, or even thyroid issues), reach out to us at the Ruscio Institute for Functional Health, where we will be able to advise you.

The Ruscio Institute has developed a range of high-quality formulations to help our patients and audience. If you’re interested in learning more about these products, please click here. Note that there are many other options available, and we encourage you to research which products may be right for you.

➕ References

  1. Basic Information about Your Drinking Water | US EPA [Internet]. [cited 2023 Apr 24]. Available from:
  2. Drinking Water Regulations | US EPA [Internet]. [cited 2023 May 19]. Available from:
  3. National Primary Drinking Water Regulations | US EPA [Internet]. [cited 2023 Apr 24]. Available from:
  4. Bond GG, Garny V. Inventory and evaluation of publicly available sources of information on hazards and risks of industrial chemicals. Toxicol Ind Health. 2019;35(11–12):738–51. DOI: 10.1177/0748233719893198. PMID: 31818239. PMCID: PMC6918022.
  5. Guidance on chemicals and health [Internet]. [cited 2023 Apr 25]. Available from:
  6. EWG Tap Water Database | EWG Standards for Drinking Water Contaminants [Internet]. [cited 2023 May 19]. Available from:
  7. Pickering AJ, Crider Y, Sultana S, Swarthout J, Goddard FG, Anjerul Islam S, et al. Effect of in-line drinking water chlorination at the point of collection on child diarrhoea in urban Bangladesh: a double-blind, cluster-randomised controlled trial. Lancet Glob Health. 2019 Sep;7(9):e1247–56. DOI: 10.1016/S2214-109X(19)30315-8. PMID: 31402005.
  8. Nadimpalli ML, Lanza VF, Montealegre MC, Sultana S, Fuhrmeister ER, Worby CJ, et al. Drinking water chlorination has minor effects on the intestinal flora and resistomes of Bangladeshi children. Nat Microbiol. 2022 May;7(5):620–9. DOI: 10.1038/s41564-022-01101-3. PMID: 35422497. PMCID: PMC9249080.
  9. Sardinha-Silva A, Alves-Ferreira EVC, Grigg ME. Intestinal immune responses to commensal and pathogenic protozoa. Front Immunol. 2022 Sep 16;13:963723. DOI: 10.3389/fimmu.2022.963723. PMID: 36211380. PMCID: PMC9533738.
  10. Lee K-S, Jeong Y-J, Lee M-S. Escherichia coli Shiga Toxins and Gut Microbiota Interactions. Toxins (Basel). 2021 Jun 11;13(6). DOI: 10.3390/toxins13060416. PMID: 34208170. PMCID: PMC8230793.
  11. Lv Z, Xiong D, Shi J, Long M, Chen Z. The interaction between viruses and intestinal microbiota: A review. Curr Microbiol. 2021 Aug 4; DOI: 10.1007/s00284-021-02623-5. PMID: 34350485. PMCID: PMC8336530.
  12. Chiu K, Warner G, Nowak RA, Flaws JA, Mei W. The impact of environmental chemicals on the gut microbiome. Toxicol Sci. 2020 Aug 1;176(2):253–84. DOI: 10.1093/toxsci/kfaa065. PMID: 32392306. PMCID: PMC7416318.
  13. Tian Y, Gui W, Rimal B, Koo I, Smith PB, Nichols RG, et al. Metabolic impact of persistent organic pollutants on gut microbiota. Gut Microbes. 2020 Nov 9;12(1):1–16. DOI: 10.1080/19490976.2020.1848209. PMID: 33295235. PMCID: PMC7734116.
  14. Fernandes A, Oliveira A, Soares R, Barata P. The effects of ionizing radiation on gut microbiota, a systematic review. Nutrients. 2021 Aug 29;13(9). DOI: 10.3390/nu13093025. PMID: 34578902. PMCID: PMC8465723.
  15. Timeline for Community Water Fluoridation | subsection title | section title | site title [Internet]. [cited 2023 May 17]. Available from:
  16. Chaitanya NCSK, Karunakar P, Allam NSJ, Priya MH, Alekhya B, Nauseen S. A systematic analysis on possibility of water fluoridation causing hypothyroidism. Indian J Dent Res. 2018 Jun;29(3):358–63. DOI: 10.4103/ijdr.IJDR_505_16. PMID: 29900922.
  17. EPA Water Health Series Filtration Facts [Internet]. [cited 2023 Apr 25]. Available from:
  18. EWG Tap Water Database | Water Filters [Internet]. [cited 2023 Apr 26]. Available from:
  19. How Long Do Water Filters Last & How Often Should They Be Changed? [Internet]. [cited 2023 May 19]. Available from:
  20. Reducing Radon in Drinking Water [Internet]. [cited 2023 May 19]. Available from:

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