Public water treatment plants add chlorine to drinking water to kill germs that cause waterborne illnesses, including cholera and typhoid. Added chlorine that effectively sanitizes contaminants is referred to as free chlorine, meaning that this chlorine is “free” to eliminate harmful microorganisms. Unfortunately, while free chlorine kills microorganisms, water treated with chlorine also contains disinfection byproducts (DBPs) such as trihalomethanes (THMs) and haloacetic acids, and these byproducts can be harmful to human health.
Several methods are available to evaluate chlorine levels in your tap water and to remove chlorine and other potentially toxic substances.
How Do I Know If My Water Has Chlorine in It?
If you notice any of the following circumstances after drinking or using tap water, your tap water may contain a high concentration of chlorine:
- Hazy or cloudy water
- Discolored water—usually yellow or brown
- Chlorine odor
- Rusty, brown stains on drains, tubs, and toilets
- Dull Hair
- Shortness of breath
- Recurring cough
How to check chlorine level in your water
If you experience any of these signs, I recommend having your water’s chlorine level checked. There are several ways you can check your water for high concentrations of chlorine and chloramine (chlorine + ammonia).
Chlorine residual test
The World Health Organization suggests a standardized test for checking the chlorine levels in your water supply, known as the chlorine residual test. This is the quickest and simplest method of determining chlorine residue. A red tablet reactant (DPD, which stands for diethyl-p-phenylenediamine) is used to color a drinking water sample in this test. The color strength is compared to standard colors on a chart to determine the chlorine concentration.
DPD is commonly used for chlorine testing, and it comes in different formats, e.g. kits, strips, drops, and tablets. The quickest way to check for chlorine in drinking water is to use a plastic test strip, similar to those used in drug and urine tests. One end of the strip is infused with a chemical compound DPD. You will notice a reaction within seconds of dipping the strip in water. If chlorine is present, the test strip changes color and is then compared to a color chart to determine the concentration level.
DPD, the same chemical compound used in test strips, is also available in tablet form. Simply dissolve a tablet in your water sample. If the reaction occurs, compare the color to a color chart to determine the exact concentration level of chlorine. These tablets come in four varieties to test different elements.
The color disc comparator is a device for measuring chlorine levels that uses DPD tablets. It is used to test for residual free chlorine in drinking water. It compares the color result to a printed chart in the same way that the other methods do. Learn more about color comparators.
This device measures the amount of chlorine in the air using light beams to measure the concentration of chlorine by the difference in colored light in different samples. For how to use the colorimeter to check chlorine levels, as instructed by Hach, a worldwide company that manufactures water analysis instruments, consult their product manual.
Why Is It Important to Remove Chlorine From Water?
According to the World Health Organization and other credible medical researchers, excessive exposure to chlorine through drinking or skin contact can cause severe health complications. The source of these complications is chlorine’s ability to react with organic compounds in freshwater to form trihalomethanes (THMs). When consumed, THMs can promote the growth of free radicals, destroying or damaging vital cells in the body. THM exposure has been linked to cancer, asthma, eczema, heart disease, an increased risk of miscarriage, and congenital disabilities, to name only a few.
Medical complications from chlorine in the water
Too much chlorine in tap water can pose a number of health risks. It’s important to consult a physician if you have any health concerns relating to the following conditions.
Chlorine may help fight waterborne diseases like cholera and typhoid, but it can also cause respiratory issues. According to a Yale University research study, while drinking chlorine-contaminated water may activate a nerve receptor that protects people by causing sneezing, coughing, and irritation, hence preventing harmful particles from entering the body, it can also cause serious problems for people with asthma.
Adults and adolescents are also at a higher risk of developing or worsening respiratory allergies due to disinfection byproducts.
However, it remains unclear if recreational swimming can aggravate well-controlled asthma.
Since chlorine dries out the skin, some of its common reactions can include itchy, red skin and hives (itchy bumps). Other symptoms may include scaling or crusting and swollen or tender skin.
This is not an allergy, but rather “irritant dermatitis” (similar to a chemical burn) caused by hypersensitivity to a natural irritant. It’s also known as “chlorine rash.” After swimming or showering, chlorine rash can cause itchy skin.
Exposure to chlorinated water can also worsen existing dermatitis, eczema, and psoriasis.
A US Council of Environmental Quality report mentioned that “the cancer risk among people who use chlorinated water is up to 93% higher than among those whose water does not contain chlorine.” Those who had been exposed to chlorinated water for 35 years or more had a higher risk of bladder cancer than those who had been exposed for less than ten years, said a study called “Case-control study of bladder cancer and chlorination byproducts in treated water,” conducted by Canadian researchers.
As researchers have classified byproducts of chlorinated drinking water as carcinogenic, some cancers are more likely to result from chlorine and its chemical derivatives than others. In addition to bladder cancer, trihalomethanes in drinking water have also been linked to colorectal cancer. Of deaths from cancer in both men and women, colorectal cancer represents the third most common.
Too much chlorine in your drinking water is not harmful to only you. It turns out to also be a life-threatening chemical to a developing fetus. Chlorine byproducts in water have been shown to increase the risk of miscarriage and premature birth. However, at what concentration level they become a problem is unknown.
You don’t need to be concerned if your drinking water contains a safe amount of chlorine. To be extra cautious, remove chlorine from water before drinking it and swim in a saltwater pool while pregnant.
How to Remove Chlorine From Water
To avoid the dangers of drinking chlorine-contaminated water, here is a comprehensive list of methods you can use to remove chlorine from your daily drinking water.
One of the easiest and most cost-effective methods for removing chlorine from water is letting it evaporate. Fill a jug or jar with your drinking water and let it rest, open, for 24 hours.
At room temperature chlorine is a gas, and it is a volatile solute in water, which means its molecules diffuse through the water and eventually escape into the air. Allowing your water to rest this way lets the chlorine evaporate. A few conditions determine how fast or slow this evaporation will occur.
The time it takes varies according to the air and water temperature. If the water is heated or boiled, the process will be faster.
Another factor to consider is the surface area per volume of water. A widemouthed container will allow the chlorine to dissipate faster because it exposes more of the water’s surface to the air.
One drawback of this method is that it only removes chlorine and not other potentially harmful water additives. Modern water treatment facilities use chloramine to purify water, also known as secondary disinfection. Unfortunately, evaporation does not effectively remove chloramine. So, first, check with your water department to see what kind of water filtering chemical they use. If they use chloramine, you must use a different method to remove chloramine, explained further below.
Distillation is a water purification method that uses heat to collect pure water in vapor. It’s highly effective in removing contaminants with a higher boiling point than water, which is the vast majority of contaminants. This method effectively removes chloramine, bacteria, germs, salts, and heavy metals such as lead, mercury, and arsenic.
Point-of-use (POU) systems are commonly used to install distillation units. They are typically installed at the kitchen faucet and purify water for only drinking and cooking. The size varies according to the amount of distilled water produced. The daily output ranges from 3 to 11 gallons.
Home stills can be placed on the counter or floor or hung on the wall. Models can be fully or partially automated, or they can be completely manual. Some units have columns or volatile gas vents to eliminate organic chemicals with lower boiling points than water, in our case, chlorine, ensuring clean water.
Distillation is ideal for those who have untreated, raw water at their disposal, and they want to remove chlorine and purify their water from all contaminants.
This method has its advantages and disadvantages. For example, it is a particularly time-consuming and slow process for water purification. Furthermore, a heat source is required for the purification to work. Despite the development of low-cost energy sources, distillation remains a costly method of purifying water.
Filtration is another method for removing chlorine from drinking water. Most water filtration systems use reverse osmosis, which uses a permeable membrane to remove chlorine and other particles, ions, and impurities from tap water. Chlorine and other contaminants are left behind when water passes through the membrane.
Reverse osmosis systems are standard in industrial use, but their application in homes is increasingly popular. In general, it takes about four gallons of water to produce one gallon of clean, filtered water.
The amount of water used in the filtration process can vary depending on the temperature of the water, the presence of contaminants, and the number of dissolved solids in the water. Because of its effectiveness, this method of removing chlorine is ideal.
The reverse osmosis process filters water by removing both good and bad minerals. After filtering everything out, a good reverse osmosis system will add in the good minerals, leaving the water cleaner and healthier than before. You must be aware of this feature before purchasing a RO filter, whether it has it or not.
Activated carbon filters, also known as charcoal filters, are made up of small pieces of carbon, either granular or block form, that are highly porous. When water passes through active carbon filters, chemicals adhere to the carbon, resulting in purer water output.
This video further explains how activated charcoal functions.
It is the only filter technology recommended by the EPA to remove all 32 organic contaminants identified, including THMs (byproducts from chlorine), all 14 pesticides (including nitrates and pesticides like glyphosate, also known as Roundup), and the 12 most common herbicides.
How NOT to Remove Chlorine From Water
UV light (ultraviolet light) is a highly effective way of removing both chlorine and chloramine from water. It uses ultraviolet light to break down these chemicals, does not affect water taste, and can exterminate them in just a few minutes. On the other hand, more exposure results in more chlorine and chloramine breakdown. These UV probes and applications can be expensive, and they do not filter out large particulates or dissolved solids.
The potential negative consequences of using this method outweigh its benefits. I do not suggest removing chlorine from your water this way.
While boiling is an effective short-term method for removing chlorine, it’s not a practical solution for daily drinking water. The average person drinks eight cups of water per day, which works out to 1/2 gallon per day and 182.5 gallons per year. Boiling gallons of water for a single-use or a family with a busy schedule is not a feasible solution.
- To ensure proper chlorine levels and to know whether you need to remove chlorine and chloramine from your drinking water, use one of the methods mentioned above to test your water for chlorine.
- To remove chlorine from water for a single person, you can boil it or use an evaporation method. You can use these methods in the comfort of your own home with little time investment, though boiling will require energy from a heating element and is not a logical long-term solution.
- Suppose you have a large family and don’t have time to boil or evaporate chlorine from your water. In that case, you should consider reverse osmosis filters or water purifiers with an activated carbon filter.
- Water distillers are ideal for people who have access to untreated water or are immunocompromised and want to remove every possible contaminant from their drinking water.
Although water treatment plants add the required amount of the water disinfectant chlorine and chloramine, to the public’s water supply, you should be aware of the chlorine level in your tap water and eliminate too much chlorine and its byproducts from your daily use of water. To avoid serious health hazards and prolonged side effects of chlorinated water, it’s wise to remove chlorine and chloramine from water, one way or another.
The procedures mentioned above may not remove 100% of chlorine, chloramine, or their byproducts from water. Still, they are highly effective methods that can prevent the dangerous consequences of high chlorine and chloramine levels.
Read more water treatment advice in our treatment section.