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It's hard to get trustworthy advice when it comes to your drinking water, so we made Tips for Taps to help answer your questions.
Order a Tap Score Water Test and receive personalized support from professional engineers and scientists by phone, email and chat.

Arsenic and Water Treatment

Testing your water and detecting arsenic is never good news, but rest assured there are reliable steps you can take to protect your health.

Arsenic is a well known human carcinogen that occurs naturally in groundwater. Public water systems are regulated by the US EPA to never exceed 10 parts per billion (ppb) of arsenic concentration, but health research demonstrates that no level of arsenic is safe to drink.

In fact, EPA proposed 5 ppb as a standard in 1996. Levels this low have shown statistically significant impacts on IQ among children, but economic requirements for setting maximum contaminant levels have kept the official threshold higher than levels harmful to health.

If you want to remove arsenic from your tap water, there are a few important things you need to know. 

What Is “Total Arsenic”?

Your total arsenic concentration is generally comprised of two common oxidation states (or forms): arsenic III (aka arsenite) and arsenic V (aka arsenate).

In drinking water, we are usually worried about Arsenic V. If you drink water with Arsenic V, however, it is quickly converted to Arsenic III–which is more toxic and bioreactive inside your body.

Arsenite and Arsenate


Does the Source of My Water Make a Difference?

The source of your water makes a difference to the amount of arsenic III versus arsenic V in your water. This matters for choosing appropriate treatment options.

If your water is coming from a community or public water treatment system and that treatment system uses chlorine for disinfection, then you can generally assume that most arsenic in your water is in arsenic V form.

If your drinking water comes from a groundwater well and there is no chlorination (or other oxidative step) installed as existing treatment, then you can’t be sure what fraction of your total arsenic is comprised by arsenic III or arsenic V.

A type of water quality test called Arsenic Speciation can help determine if your total arsenic is mostly arsenic III or arsenic V. 


Test your water for arsenic 

Does Reverse Osmosis Remove Arsenic?

Reverse osmosis water treatment technology can reliably remove arsenic V but does not reliably remove arsenic III.

If your water’s arsenic is all or mostly arsenic V then you can reliably use reverse osmosis technology to remove arsenic from your drinking water.

If your water’s arsenic is mostly comprised of arsenic III then you will either need a special treatment technology OR you will need an additional treatment step to oxidize arsenic III to arsenic V before using reverse osmosis for treatment.

Reverse osmosis is not the ONLY method of arsenic removal, companies like AdEdge and others provide other ion exchange and filtration-based treatment options.

Do I Need Whole Home Water Treatment to Remove Arsenic?

Whole home water treatment for arsenic removal is NOT necessary unless you regularly drink water from many of the taps in the house.

You can safely choose to treat only the water you ingest or use for drinking by installing a point of use filter at your main water source in the home or building (like under your kitchen sink). This can save thousands of dollars, because according to public health research, arsenic does not show an appreciable impact on health via showers, tubs, or brushing teeth (unless concentrations are enormous, >1,000 parts per billion).

It is important to note that no treatment technology can ever truly remove a contaminant 100%. Water treatment with reverse osmosis can remove arsenic as much as 98%, however. Most professionals and public health research suggests trying to reduce arsenic intake by drinking water to less than 3 parts per billion. 

What to Do If You Have Arsenic in Your Well Water?

Tap Score's network of laboratories and water experts can help. We're an independent and unbiased testing service without partnerships in the treatment industry. 

Chat with us to find the right treatment system

Test your water for arsenic 

Lab Testing


It's hard to get trustworthy advice when it comes to your drinking water, so we made Tips for Taps to help answer your questions. Order a Tap Score Water Test and receive personalized support from professional engineers and scientists by phone, email and chat.


Aug 13, 2020 • Posted by Tap Score

Hi Boyd — Tap Score team here. We include arsenic testing in most of the testing packages. It is perhaps the case that your test package either (1) didn’t include arsenic or (2) included arsenic but the arsenic was Non Detect and so not showing up in your Health Watch List. If you or others have questions like this, you can always hit the little chat bubble on the bottom of your screen and someone on the Tap Score team will be with you to help right away!

May 14, 2020 • Posted by Boyd Wolford

I just received your lab report and there’s nothing pertaining to arsenic at all. Why not? I would think it should be listed with the other analytes.

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