Does Reverse Osmosis Remove Chlorine?

Does Reverse Osmosis Remove Chlorine_Best Home Chlorine Treatment Filter

If you’re worried about the amount of chlorine reaching your water supply, then you have probably considered removal methods like reverse osmosis. But does reverse osmosis remove chlorine or are there any better options?

This article will discuss what you must know about reverse osmosis and if an RO system can actually remove chlorine effectively.

Chlorine in Drinking Water: Is It Safe to Drink?

Water comes from different sources like wells and lakes, all of which may be contaminated with germs or bacteria that cause sickness. Water can also become contaminated as it flows through pipes and into our faucets. To prevent that from happening, municipalities and water companies add disinfectants, with the two most popular ones being chlorine and chloramine. 

We’ve all heard of the importance of adding chlorine to swimming pools but finding it in tap water is a whole different issue. Chlorine is a gas dissolved into water to kill microorganisms entering water supply piping. This has been the primary disinfectant, though.

Does Reverse Osmosis Remove Chlorine_Best Home Chlorine Treatment Filter Infographic
Chlorine and Chloramine Water Treatment Effects

What Is Chloramine?

On the other hand, chloramine is chlorine mixed with ammonia. Ammonia will bind the chlorine gas, keeping it in the solution for longer periods. 

Both chlorine and chloramine work to kill bacteria, parasites, and viruses in water. Nowadays, chloramine is becoming a more popular option as it stays active in water for longer and doesn’t have much of a chlorine taste or odor.

What Are The Health Concerns?

While both are added to water to limit bacterial growth and hazardous contaminants, there are concerns. For instance, these two disinfectants can be an issue for those who have respiratory issues or receive dialysis treatment. They are also harmful to aquatic animals. 

Note that chlorine levels of up to 4 milligrams per liter are considered safe for consumption [1]. Studies have also shown that tap water with chloramine levels less than 4 mg/L did not create negative health effects [2]. A normal chloramine disinfection level in drinking water can range from 1.0 to 4.0 mg/L. Anything over that may cause serious health effects. 

How Does Reverse Osmosis Remove Chlorine?

Enter the reverse osmosis system, a water treatment process working at a molecular level. This means that RO systems have a filter membrane for only water molecules to pass through, allowing you to have clean, pure water. RO systems have semi-permeable membranes so water impurities cannot pass through the pores, being trapped on one side while the water molecules move to the purer side.

RO Filtration Stages

Chlorine and chloramine can’t be removed with the RO semi-permeable membrane filter alone. To solve this, RO systems feature activated carbon pre-filters to help remove chlorine before passing through the membrane. Most reverse osmosis systems have anywhere from three to ten stages of filtration. It’s easiest to understand by looking at an example of a typical multi-stage RO system. Water will pass through the following stages during the RO filtering process:

Does Reverse Osmosis Remove Chlorine_RO System Diagram Infographic
RO Filtration Stages
  1. Sediment Pre-Filter: The sediment pre-filter is the first line of defense at removing large debris like rust, dirt, and sand.
  2. Activated Carbon Pre-Filter: The activated carbon filter usually contains a negative charge to help attract contaminants. This stage is best for eliminating chlorine, bad taste and odor before the water reaches the reverse osmosis membrane.
  3. Polypropylene Pre-Filter: This stage is typically a filter with pores 1 micron or small to catch as many particles and contaminants as possible before reaching the RO membrane.
  4. RO Membrane: The pressure forces water molecules through the reverse osmosis membrane pores that are 0.0001 micron to filter out harmful contaminants.
  5. Activated Carbon Post-Filter: Just as the first carbon filter removes chlorine and unwanted contaminants, the post-filter removes any remaining impurities before the water is dispensed.
  6. Water Storage Tank: The water storage tank holds the filtered water until the system faucet is turned on.

As mentioned above, each RO system is different and can have a varying number of filtration stages. The above diagram is of course for a tank-based RO filter. There are also tankless RO systems available, which have some differences that we discuss in our tankless vs tank RO article. Other potential filters that can be included with the systems would be a remineralization filter to add minerals, or a UV light sterilizer to kill bacteria.

How Much Chlorine Does Reverse Osmosis Remove?

When using carbon block filters in RO systems, they can remove up to 99% of chlorine in water. Carbon pre-filters will absorb chlorine in the filtering process while preventing RO membranes from damage when in contact with chlorine. This is important to note as the membranes are extremely sensitive and may incur damage from chlorine. That’s why reverse osmosis can’t remove chlorine, requiring carbon filters to perform that task. 

So, does reverse osmosis remove chlorine? No, reverse osmosis alone does not remove chlorine. Carbon filters included in modern reverse osmosis filters and systems are responsible for this. If a reverse osmosis system doesn’t feature a carbon filter, it won’t be able to remove chlorine in your water.

How to Test for Chlorine in Water at Home

Chances are if you live in the city, you will have some amount of chlorine or chloramine. But also, if you have well water with a chlorine injection system or if you recently shocked your well water with chlorine, you need to know the amount of chlorine in your water. To determine how much chlorine and chloramine you may have in your water, try any of these methods:

DIY Home Water Test Kits

People can test their home’s waters themselves through DIY test kits or strips, which are affordable and effective. These strips rely on color coding after dipping the strip into your water source. Depending on how dark the test strip color turns will determine the amount of chlorine concentration in your water. The drawback to this method is it is not very accurate, and you don’t get a precise measurement. We recommend using these for “spot checks” in between a more thorough lab test.

Lab Test from Tap Score

This is our most recommended method to test for chlorine. Using water samples from your home to submit for a Tap Score lab test offers the most accurate reading of chlorine levels in your water. Far more accurate than the prior mentioned DIY test strips, Tap Score will give you a precise reading of your chlorine and chloramine levels (in addition to dozens of other contaminants). Also, every home and location is different. So while you can look at your city’s water test results, it is not the same as getting an accredited lab test for your home.   

Environmental Working Group Database

You can head over to EWG’s water database and input your ZIP code or state. From there, you can get a report on estimated contaminants detected in your area’s drinking water, including chlorine. 

Consumer Confidence Reports 

The Environmental Protection Agency requires every city to publish its local water test results every year. These tests are known as Consumer Confidence Reports (CCR), or water quality reports. These reports share the area’s quality of tap water.

Alternative Methods to Remove Chlorine and Chloramine

There are various ways to remove chlorine from water, including:

Boiling Water

Boiling water can effectively remove all free chlorine from tap water, though it’s a slightly lengthy process, depending on how much water you have. You need to fill a kettle or pan, turn on your heating element, wait for it to boil then cool it before use. 

Granular Activated Carbon

Granular activated carbon (GAC) filters can remove chlorine and other organic chemicals from tap water. GAC is made of raw organic materials high in carbon, like coal or coconut shells. Activated carbon can remove chemicals dissolved in water by trapping and absorbing the chemical [3]

Water Distiller

A water distiller will remove chlorine and chloramine from your tap water. The distillation process boils the water and collects the steam vapor. This process makes some of the purest drinking water available, however, it ends up with a flat taste because it removes the minerals. Similar to RO water, adding minerals back is possible with a remineralization filter or mineral drops.

Although distilling water takes considerable time, one advantage is that you can make it at home for free since it is a natural process.

The Drawbacks of Reverse Osmosis Systems

Reverse osmosis systems would also have disadvantages that are important to note, such as:

Wastes Water

One of the drawbacks of using an RO filter system is it “wastes” water. The average system will use 4 gallons of water to create one gallon of purified water. Fortunately, as technology has evolved, reverse osmosis waste water has declined considerably. There are now efficiency systems that will create two gallons of purified water using only one gallon of waste water.

Filter Replacement Costs

Like all filtration solutions, reverse osmosis systems will require maintenance and filter replacement to ensure it performs their best. Not only will you spend time and effort on maintenance and filter replacement, but money on purchasing filters. You will need to replace the pre and post-filters about every 6 months, but the RO membrane should last for over a year. Make sure to factor in the full cost of the RO filtration system before making a decision.

Removes Healthy Minerals

While the reverse osmosis membrane can remove harmful contaminants, it can also remove healthy minerals including calcium, potassium, magnesium, fluoride, and other bicarbonates. These minerals are helpful for our overall health. Moreover, removing these minerals would mean that the treated water’s pH levels decrease, resulting in higher acidity levels. The good news is there are many ways to remineralize RO water.

Expensive Price

The initial cost of reverse osmosis systems can be high, along with the maintenance required in the long run, as mentioned above. Don’t be intimidated, though. There are plenty of RO options that cost as little as $200 dollars and are easy to maintain. That said, there are under sink RO systems that can cost well over $1,000. And a whole house reverse osmosis system will start at $3,000. It’s about finding the best fit for your specific needs.

Requires Installation

Point-of-use reverse osmosis systems will require installation under your sink. While it’s possible to do this yourself, it can be a little tricky, especially if you aren’t familiar with how to install these systems. If you don’t want to deal with installation, you can always go with a countertop RO unit that only needs to be plugged into your outlet.

FAQs For Reverse Osmosis Chlorine and Chloramine Removal

Does reverse osmosis remove chlorine and fluoride?

Reverse osmosis does not remove chlorine unless it has activated carbon filters. However, it will remove fluoride and other minerals, like iron, calcium, and manganese. If a RO filtration system includes a CAG filter, it can remove up to 99% of chlorine and fluoride.

Does reverse osmosis remove chloramine?

Like chlorine, reverse osmosis membranes do not remove chloramines. Chloramines are removed from the filters included in reverse osmosis systems, particularly activated carbon.

Why is chlorine added to drinking water?

Chlorine is added to drinking water as a disinfectant to prevent germ contamination. It can kill disease-causing germs like norovirus, salmonella, and campylobacter. 

Is there a safe or healthy level of chlorine consumption?

Yes, people can consume up to 4 milligrams of chlorine per liter of water. This is considered safe for human consumption and won’t likely cause harmful effects.

Article Sources

Freshnss uses only the highest-quality sources to support the facts used in our articles including: government organizations, independent studies, peer-reviewed journals, and lab testing results. Read our editorial review guidelines here to learn more about how we verify and fact-check our writing to keep our content reliable, accurate, and trustworthy.

  1. Drinking Water Regulations, US Environmental Protection Agency (EPA)
  2. Some Drinking-water Disinfectants and Contaminants, including Arsenic, National Institutes Of Health (NIH)
  3. GAC to BAC: Does It Make Chlorinated Drinking Water Safer?, Journal Of The International Water Association
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