While chlorine is commonly used to disinfect water and eliminate harmful bacteria, an excessive amount can have adverse effects on human health. As water utilities ramp up disinfection methods, it is increasingly important to understand how to test for chlorine in water to ensure your safety.
In this article, I’ll share everything you need to know about chlorine in drinking water, including why it’s added, how to test for chlorine, and how to remove it.
- The best method to test for chlorine in drinking water is with a certified lab test that scans for chlorine, chloramine, and disinfection byproducts.
- The fastest and easiest technique to determine chlorine levels in drinking water is a color test strip, however, they do not provide a precise measurement.
- The EPA maximum chlorine level in drinking water is 4.0 PPM to ensure effective disinfection while still being safe to consume.
Why Is Chlorine Added To Drinking Water?
Chlorine is added to water by municipal water suppliers for its disinfectant properties, a process known as “chlorination”. Its ability to kill harmful microorganisms, such as bacteria and viruses, makes it an effective tool in water treatment.
Thus, chlorine works by breaking down the cell walls and proteins of these pathogens, rendering them harmless. This process helps protect us from waterborne diseases like cholera typhoid, hepatitis, and giardiasis.
What Is Free Chlorine, Combined Chlorine, and Residual Chlorine?
Chlorine is added to drinking water primarily for its disinfectant properties, effectively killing bacteria and viruses. However, excessive chlorine levels can be a cause for concern. Understanding the different forms of chlorine is essential to comprehending water test results:
Free chlorine refers to the chlorine that remains available in the water for disinfection purposes. It is in its most active and potent form, effectively killing bacteria, viruses, and other microorganisms. Free chlorine can be present in the form of hypochlorous acid (HOCl) or the hypochlorite ion (OCl-), depending on the pH level of the water.
Residual chlorine, also known as total chlorine, refers to the total concentration of chlorine compounds present in the water. It includes both free chlorine and combined chlorine. Residual chlorine serves as a measure of the overall chlorine content in the water and indicates the effectiveness of disinfection.
Combined chlorine, also referred to as chloramines, is formed when chlorine combines with organic or nitrogenous compounds present in the water. Unlike free chlorine, combined chlorine is not as effective as a disinfectant and has a distinct odor commonly associated with swimming pools. High levels of combined chlorine can lead to eye and skin irritation and contribute to the formation of harmful disinfection by-products.
What Is The Safe Level Of Chlorine In Drinking Water?
The Environmental Protection Agency has set the federal MRDL for chlorine in drinking water at 4.0 mg/L. This is the maximum concentration of disinfectant allowed in tap water.
Generally, a free chlorine residual of 0.2 mg/L is the minimum effective concentration to control microbial growth in the distribution system.
Signs That There May Be Chlorine In Your Water
Fortunately, chlorine in water can be detected with basic human observations. If you identify one of the below signs, it is time to test your drinking water for chlorine to determine the exact level present:
- Strong chlorine odor: A strong smell of chlorine in your tap water can indicate the presence of chlorine disinfectants.
- Chlorine taste: If your water tastes like chlorine, it suggests the presence of chlorine compounds in the water.
- Bleaching effect: Chlorine can have a bleaching effect on fabrics and surfaces. If you notice discoloration or fading of clothes or fixtures, it could indicate the presence of chlorine in your water.
- Skin and eye irritation: High chlorine levels in water can cause skin dryness, irritation, or redness, as well as eye irritation or redness after showering or bathing.
How To Test For Chlorine In Water
Testing the chlorine levels in your water is crucial to ensure its quality and safety. There are several methods available for testing chlorine, ranging from certified laboratory water tests to DIY options such as chlorine test strips and pool test kits. Let’s explore these methods in detail:
Certified Laboratory Testing
A certified laboratory water test is the most comprehensive and accurate method to determine the chlorine content in your water. It involves collecting a water sample and sending it to a certified laboratory for analysis.
I recommend using the Freshnss Labs water test kit that scans for chlorine and other common city water contaminants. The kit comes with everything to properly collect a water sample and send it to a certified laboratory. The lab will then perform professional testing to measure chlorine and disinfection by-products.
Proper Steps For Collecting A Water Sample For Lab Testing
- Collect the water sample from your primary drinking water faucet. You may need to clean the faucet’s screen first to ensure accurate results.
- Turn on your cold water and let it run for 30 – 60 seconds to flush the system before collecting your sample. Alternatively, you may take the water sample immediately to test for the first draw.
- Wear clean rubber gloves if you have them available to avoid cross-contamination.
- Turn on the cold water supply and slowly fill the sample bottle so it does not overflow.
- Make sure the sample bottle is filled to the shoulder of the bottle and the vials all the way to the top.
- Carefully package the sample bottle as instructed and submit them to the lab to be analyzed by a certified professional.
- Within 3 business days, you will receive your test results including the exact chlorine levels in your water.
DIY Chlorine Test Strip
DIY chlorine test strips are a convenient and affordable option for testing chlorine levels at home. The chlorine test strip contains chemical reagents that react with chlorine and change color, allowing you to measure the chlorine concentration.
To use chlorine test kits, simply dip the test strip into your water sample and wait for 30 – 60 seconds. Then remove the test strip and compare it to the provided color chart to measure the chlorine concentration.
Digital colorimeters are digital devices that can measure free chlorine, total chlorine, and residual chlorine levels in water. They utilize photometric technology to analyze the color change that occurs when a chlorine-reactive reagent is added to the water sample with light beams. These devices are expensive and are typically used for professional field use.
DPD Color Tablets
DPD (N,N-Diethyl-p-Phenylenediamine) color tablets are another method for testing chlorine levels. These tablets contain DPD reagents that react with chlorine and produce a color change. By comparing the resulting color with a reference chart, you can determine the chlorine concentration in the water.
There are four types of tablets to detect different disinfectant chemicals:
- DPD 1: For Free Chlorine
- DPD 2: For combined chlorine
- DPD 3: For total chlorine
- DPD 4: For total available chlorine
Pool Test Kits
This method involves the utilization of a liquid chemical known as orthotolidine. Swimming pool test kits alter the color of drinking water to a bright yellow shade. To utilize a pool test kit, you should fill the bathtub with water and add two to three drops of the provided solution. Allow the water to undergo a color change. It is important to remember that this test solely indicates the presence of chlorine and does not measure the amount of free chlorine.
Should I Test My Water For Chlorine?
Testing your water for chlorine is highly recommended to create a historical record of your water quality and ensure its safety. Testing frequency should be expedited under the following circumstances:
- High-Risk Individual: Some individuals may be sensitive to chlorine or have certain health conditions that make them more susceptible to its effects.
- To Confirm Proper Chlorine Levels: If your Water Quality Report indicates a concerning amount of chlorine levels in your water, testing for chlorine helps ensure that your water meets the recommended EPA disinfection standards to treat harmful microorganisms.
- Following A Boil Advisory: If your water supplier issues a boil advisory, it is suggested to test your water following the advisory for excessive chlorine present.
- After Well Shock Disinfection Treatment: If you have shocked your well for disinfection purposes, you should test your water to ensure the chlorine level is safe before using it again.
- Strong Odor And Taste: If you observe telltale signs that your water has too much chlorine like a chemical taste strong odors.
Negative Effects Of Combined Chlorine and Free Chlorine In Water
When it comes to water quality, the presence of excessive chlorine can have detrimental effects on both our health and the overall water supply. Below are some of the symptoms and negative effects associated with high chlorine levels:
Skin And Eye Irritation
Prolonged exposure to chlorinated water during bathing or swimming can cause skin to become itchy, flaky, and uncomfortable. Additionally, chlorine can irritate the eyes, resulting in redness, itchiness, and even blurred vision.
Inhaling chlorinated water vapor or steam, particularly during showers or baths, can irritate the respiratory system. This irritation may lead to coughing, wheezing, shortness of breath, and exacerbation of existing respiratory conditions such as asthma or bronchitis.
Hair And Scalp Problems
Chlorine has a drying effect on hair and scalp, stripping away natural oils and leaving hair feeling brittle, dry, and prone to breakage. It can also cause scalp irritation, itchiness, and dandruff.
Disinfection By-products (DBPs)
When chlorine reacts with organic matter, such as bacteria, algae, or natural compounds found in water sources, disinfection by-products (DBPs) can form. DBPs include trihalomethanes (THMs) and haloacetic acids (HAAs), which are known to be harmful to human health. Prolonged exposure to DBPs has been associated with an increased risk of cancer, reproductive issues, and developmental problems.
Unpleasant Taste and Odor
Higher concentrations of chlorine in water can result in an unpleasant taste and odor, making it less appealing for drinking or cooking purposes. The strong chlorine taste and odor can negatively impact the overall quality and enjoyment of water.
How Do You Remove Chlorine From Tap Water?
While chlorine serves an important role in ensuring water safety, many individuals prefer to remove it from tap water due to its potential health effects. When searching for the best water filter to remove chlorine, it is preferable to find a filter certified to NSF/ANSI 42 standards which ensures the reduction of monochloramine from 3.0 ppm down to < 0.5 ppm in a water sample.
The following are the effective methods to remove chlorine from water:
Catalytic Carbon Filters
Activated carbon (AC) water filters have the affinity to decrease levels of chlorine in water due to their porous structure. However, catalytic carbon filters are a superior option for removing chlorine and chloramine from tap water. These filters have a modified carbon surface that creates catalytic sites which are capable of removing up to 4 times more chlorine than unmodified activated carbon media.
The catalytic carbon used in these filters has enhanced properties that make it even more efficient at removing chlorine. The water passes through the carbon filter, and the chlorine molecules adhere to the carbon surface, resulting in chlorine-free water.
Carbon filters come in a variety of sizes. The easiest and least expensive option is to use a water filter pitcher tested to remove chlorine. Alternatively, you can use a whole house filter which protects every fixture in your home including showers, drinking water, and washing machines.
Reverse Osmosis Systems
A reverse osmosis system has the capability to completely remove combined chlorine, residual chlorine, and free chlorine from drinking water. These systems use a semi-permeable membrane that allows water molecules to pass through while trapping larger molecules, such as chlorine ions. Importantly, the RO system needs to include a carbon pre or post-filter to effectively remove the chlorine and protect the membrane.
Water distillation is another method to remove chlorine from tap water. Distillation involves heating the water to create steam, which is then condensed and collected as purified water. Since chlorine has a lower boiling point than water, it evaporates with the steam and is left behind during the evaporation process. The collected distilled water is free from chlorine and other contaminants.
However, it is important to consider that distillation can remove beneficial minerals along with chlorine, so remineralization may be necessary.
Frequently Asked Questions
Is it safe to shower in water with high levels of chlorine?
Showering in water with high levels of chlorine is generally safe, however, prolonged exposure to chlorine may cause skin and hair dryness or irritation. Using a shower filter can help mitigate these effects.
Do I need to test for chlorine if I have well water?
Chlorine is typically not present in well water unless intentionally added. However, it is still recommended to periodically test well water for other potential contaminants based on local regulations and recommendations.
Does boiling water remove chlorine?
Boiling water can reduce chlorine in drinking water, but it is not the most effective method. Chlorine evaporates at a lower boiling point than water, but prolonged boiling can result in significant water loss. Consider using activated carbon filters or other water treatment methods for more efficient chlorine removal.