Does Reverse Osmosis Remove Chlorine from Drinking Water?

Does Reverse Osmosis Remove Chlorine from Drinking Water?

Are you a homeowner with high levels of chlorine in your drinking water. If so, you may be wondering if reverse osmosis can remove chlorine.

Reverse osmosis systems can remove 99% of chlorine from drinking water. However, chlorine is a strong oxidizer that will quickly damage the RO membrane, rendering it ineffective at reducing chlorine. Fortunately, most reverse osmosis systems include a carbon filter that removes all of the chlorine to protect the membrane. A reverse osmosis unit will remove all of the chlorine from tap water – but the chlorine is removed by the activated carbon pre-filter and not the RO membrane.

Reverse osmosis systems are very effective at removing chlorine from tap water. However, the reverse osmosis filter membrane doesn’t remove the chlorine – the activated carbon filter does. If you want to learn more about chlorine and how to remove it from drinking water, continue reading. We cover reverse osmosis, how it removes chlorine from water, and a lot more.

About Chlorinechlorine in drinking water

Chlorine is added to public drinking water supplies to kill bacteria and other microorganisms that can cause disease. Although chlorine is effective at disinfecting water, it gives the water a chemical taste. Some people are sensitive to chlorine and may experience skin irritation, respiratory problems, and other adverse health effects when

What is chlorine and why is it in my water?

Chlorine and chloramine are disinfectants frequently used to destroy water-borne bacteria and viruses. These chemicals are added by public water utilities to ensure that water delivered to homes and businesses is safe to drink.

It’s a safe bet that most homes in the United States have chlorine in their tap water, given that 86 percent of American households get their drinking water from a municipal provider.

Health concerns with chlorine

Despite the advantages of chlorine and chloramine, new concerns have arisen about their side effects in drinking water. Many families, in fact, want to get rid of chlorine and chloramine from their tap water.

While chlorine is effective at disinfecting water, it does have some negative side effects. Some people are sensitive to chlorine and may experience skin irritation, respiratory problems, and other adverse health effects when exposed to chlorinated water.

Although chlorine disinfects water, it also reacts with organic matter in the water to form potentially harmful by-products called trihalomethanes (THMs) and haloacetic acids (HAAs). These compounds have been linked to cancer and other adverse health effects.

Taste and odor issues with chlorine

Many people find that water treated with chlorine has an unpleasant taste and odor. This is because chlorine reacts with organic matter in the water, to form chloroform and other chemicals that have a strong, unpleasant odor.

One of the most common complaints is that chlorine treated water smells like a swimming pool. Other people note that it has a strong, chemical taste that can make it difficult to drink.

Drinking water standard for chlorine

According to the CDC, chlorine levels up to 4 mg/L or 4 ppm are considered safe in drinking water. At this concentration, there is little risk of negative health consequences.

Reverse Osmosisreverse osmosis filter system

Reverse osmosis is a widely used treatment method that reliably removes a wide range of contaminants from drinking water. It is effective at reducing the concentration of many impurities such as lead, PFAS, and heavy metals.

How RO works

Reverse osmosis systems use a semipermeable membrane to filter impurities from water. The membrane allows water to flow through while trapping dissolved solids and other contaminants. The system applies pressure to the water, forcing it through the membrane and removing any impurities.

The membrane is constructed of a semi-permeable polymer that is spirally wrapped around a central tube. The water is forced through the membrane, and the impurities are filtered out. The clean water is then collected on the other side of the membrane, while the contaminants are retained in a concentrated brine. This brine waste is then flushed down the drain.

Reverse osmosis systems can be used to treat both municipal water supplies and private wells. This treatment technology is effective at removing a wide range of contaminants, including salt, bacteria, viruses, pesticides, and more.

RO system components

Reverse osmosis systems typically consist of three modules:

1.   pretreatment

2.   reverse osmosis membrane

3.   post-filter

RO Activated Carbon FilterPretreatment protects the membrane from fouling and damage caused by chlorine. It usually consists of a sediment filter and an activated carbon filter. The sediment filter removes particles such as dirt and rust, while the activated carbon filter removes chlorine and other chemicals.

The reverse osmosis membrane is the heart of the system. It’s a thin film composite (TFC) that remove contaminants from water. The TFC is made of several layers of material, including a semi-permeable membrane.

The post-filter is the final stage of filtration that removes any remaining impurities from the water. This is typically a second carbon filter that ensures the water is safe to drink and tastes great. It also includes a particle filter to remove any remaining turbidity.

Some RO systems include a water storage tank, which stores the clean water until you’re ready to use it. This is desirable because the flow rate through the filter is slow. Having a storage tank ensures you can fill a glass or a cooking pot quickly with clean water without having to wait.

How Well Does Reverse Osmosis Treat Chlorine

Reverse osmosis filters remove essentially all of the chlorine in tap water. This is because the activated carbon filter removes the chlorine before it reaches the RO membrane. The RO membrane itself does not remove chlorine – only dissolved solids such as salt.

How much chlorine can reverse osmosis remove

A reverse osmosis system can remove 99% or more of the chlorine in your tap water. A well-maintained, high-efficiency RO system will remove 99.99% of the chlorine.

It is important to note that the reverse osmosis part of your RO system isn’t actually removing the chlorine. The chlorine is removed during the pre-treatment process by the activated carbon filter.

Challenges with chlorine and RO

Chlorine is a powerful oxidizer. This is why it’s used to disinfect our drinking water. It also damages the membrane in your reverse osmosis filter.

To protect the membrane, virtually all RO systems include an activated carbon filter to remove the chlorine. Activated carbon is extremely effective at removing chlorine. The US EPA considers activated carbon a benchmark technology to evaluate how well other treatment methods perform.

It is accurate to say that reverse osmosis filters remove chlorine. However, the “work” of removing the chlorine is done by the activated carbon filter and not the reverse osmosis membrane.

Factors to Consider with Reverse Osmosis

If you’re concerned about the quality of your drinking water, a reverse osmosis filter may be a good option for you. RO filters are able to remove a variety of contaminants from your water, including lead, mercury, and chlorine. However, there are a few factors you should consider.

Installation cost of reverse osmosis

Depending on your home’s plumbing, installing an RO system can be relatively simple or quite complex. If your home has a standard under-sink configuration, you can likely install the filter yourself. However, if your home has multiple faucets or you need to drill new holes for the filter, it’s best to hire a professional.

A whole-house RO system can be expensive to install, especially if you have to modify your home’s plumbing. An under-sink unit, on the other hand, can often be installed by a good do-it-yourselfer for a reasonable cost. Each home is unique, so you’ll have to determine which system is right for you.

Maintenance cost

RO filters have sediment filters and activated carbon filters that have to be replaced. A sediment filter will usually last for about six months before it needs to be replaced. Carbon filters have to be replaced every 3 to 6 months, depending on how much water you use and the amount of chlorine in your water.

The cost of replacement filters can vary, but you can expect to spend around $60 to as much as $200 per year on them. Whole house filters are 3 to 4 times as much as under-sink filters.

While this may seem like a lot, it’s important to remember that RO filters can remove a variety of contaminants from your water, making it safer and healthier to drink.

Whole-house versus under-sink unitsWhole House RO System Diagram

Another thing to consider is how much water you’ll need to filter. RO filters are typically sized according to the number of gallons they can process per day. If you have a large family or use a lot of water for cooking and bathing, you may need a larger filter.

Reverse osmosis systems are available in a wide range of sizes, from small countertop units to large industrial systems. They can be used for point-of-use (POU) applications, such as filtering water for a kitchen sink, or point-of-entry (POE) applications, such as filtering all the water coming into your home.

Deciding which type of RO system is right for you depends on a number of factors, including your budget, the size of your home, and your water quality. Read my article on under-sink RO systems and whole-house RO systems for a detailed explanation.

NSF certification

Reverse osmosis filter manufacturers often make claims about how well their units remove contaminants. The best way to be certain of their claims is to look for units that have been certified by NSF International.

NSF is an independent organization that tests and certifies products to ensure they meet strict standards for quality and safety. If a product has been certified by NSF, you can be confident it will perform as advertised.

The applicable standard for point-of-use reverse osmosis systems is NSF/ANSI 58. It covers the following parameters:

  • Materials of construction and leaching of harmful substances
  • Mechanical integrity
  • Removal of total dissolved solids (TDS)
  • Efficiency rating
  • Recovery rating
  • Contaminant concentration reduction


Does activated carbon remove chlorine?

Activated carbon is one of the most effective ways to remove chlorine from tap water. It is a benchmark technology for chlorine treatment. The activated carbon pre-filter in a reverse osmosis system is where the chlorine is removed, not the RO membrane.

Does boiling water remove chlorine?

Boiling water is an effective way to remove chlorine from water. The chlorine is volatized when water is boiled, and it escapes into the air.

Does a water softener remove chlorine?

A water softener will not remove chlorine from water. The media in a softener is designed to remove calcium and magnesium, the two minerals that are known as hardness.

Do Brita Filters remove chlorine?

Brita filters remove chlorine from tap water using activated carbon to trap chlorine molecules as water passes through the filter, resulting in better-tasting and odor-free water. Read my comprehensive article about the topic do pitcher filters remove chlorine.

Do PUR filters remove chlorine?

PUR filters are designed to remove chlorine from tap water, effectively reducing the taste and odor of chlorine in drinking water. PUR filters use activated carbon to capture chlorine molecules and other harmful compounds and minerals from water, providing clean and fresh-tasting water for your home. Regularly replacing the filters is essential to ensure the continued removal of chlorine and other contaminants from your water.


If you’re a homeowner concerned about chlorine in your drinking water, you may want to consider investing in a reverse osmosis system. RO systems are an effective way to remove a variety of contaminants from your water, including chlorine.

When shopping for an RO system, be sure to look for one that has been certified by NSF International. This will ensure that the unit meets strict standards for quality and safety.

Installing an RO system is a big investment, but it’s one that can pay off in the long run by providing you and your family with safe, clean drinking water.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children.

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