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Does Chlorine Evaporate from Tap Water? (Quick Answer!)

Scott Winfield
Written by Scott Winfield
Last Updated on

So, you’re wondering if chlorine evaporates from tap water. The short answer is yes, it does.

This is because chlorine is slightly volatile, meaning it will evaporate slowly from the water’s surface if left still for 1–5 days.

But are there faster ways to evaporate chlorine from tap water?

Does Chlorine Evaporate from Tap Water? (Quick Answer!)

In this guide, we’ll answer this question in great detail, and take a close look at some other key points.

How Long Does It Take For Chlorine To Evaporate From Water?

Tap Water

It takes approximately 1–5 days for chlorine to evaporate from water if kept in a storage unit. However, the process depends on the volume of the water that needs to be dechlorinated and the chlorine concentration.

If the chlorine concentration is too high, the evaporation process might pass the five-day mark. However, the chances that your tap water has that much chlorine are very low.

Although up to 4 mg of chlorine per liter is deemed to be safe by the CDC, tap water across the USA mostly has 1–3 mg/L of this disinfectant. As long as the level of chlorine in the water is in that range, it won’t take more than five days to evaporate since 2 mg/L takes only four days to evaporate completely.

Several methods, such as boiling, aeration, or exposing the water to ultraviolet light, can also shorten the evaporation period. We’ll cover all these methods and more in depth shortly.

The Importance of Water Dechlorination

When added to water, chlorine removes disease-bearing contaminants like bacteria. However, high chlorine concentrations in water can cause long-term health issues like congenital anomalies and even bladder cancer. Moreover, even safe concentrations of chlorine can be unpleasant for some due to its bleach-like odor and taste.

So, how do you tell if the levels of chlorine in your drinking water are safe?

The answer is testing. You can test your water by either purchasing a home water testing kit or by sending a water sample to a certified lab.

At-home test kits are affordable and very easy to use. Typically, you simply dip a test strip in a glass of water and wait for it to change color. Then, you compare the color of the strip to the provided color chart. The downside is that these tests don’t tend to be very accurate.

The most reliable way to get accurate results is to send a sample to an EPA-certified lab. You may have to wait a few days to get your results, and it’s more expensive than using at-home test kits, but the accuracy is more than worth it.

You can also implement certain CDC-approved tests. These tests vary from inexpensive methods such as pool kits to expensive but highly reliable tools like digital colorimeters.

6 Faster Ways to Remove Chlorine From Your Water

Evaporation is one of the best methods to eliminate chlorine from water. However, although it’s quite easy, waiting 4 to 5 days to have a cup of drinking water isn’t practical. Fortunately, there are several alternative methods that are quicker. We recommend using a water filter.

1. Boil the Water


Boiling is one of the quickest and most effective ways to remove chlorine from water.

For every eight minutes you boil the water, 1 mg/L of chlorine evaporates. So, just to be sure that all the chlorine is removed, it’s best to leave the water boiling for at least 20 minutes.

Boiling also removes other harmful disinfectants and contaminants from the water, including chloramine. Having said that, removing chloramine via boiling may take a little longer since it’s considerably less volatile than chlorine.

2. Use Water Aeration

Water Aeration

Water aeration is a process in which large amounts of air pass through the water and gather contaminants such as dissolved gasses, ultimately venting them out. Although it’s a more complex procedure that requires you to install a system, it’s less efficient than boiling because it takes 12-24 hours to dechlorinate the water.

However, for those who want to dechlorinate their aquariums or need a dechlorinating method for industrial purposes, aeration is more beneficial, as it can deal with large volumes of water.

3. Install a UV Light System

Kind Water UV Filter
Best of UV Water Purification

Although ultraviolet light filter systems can be expensive, they are by far the most efficient way to eliminate chlorine since UV rays can remove 5 mg/L of chlorine in a matter of minutes.

If you want to evaporate chlorine from water with a UV light manually, here’s how to do it:

  • First, you’ll need to fill up a storage tank with water and install a UV lamp.
  • Once you’ve installed the bulb, you should ensure the UV rays point directly to the tank.
  • To remove the chlorine, you need a UV light wavelength of about 180-400 nanometers for every square cm of water and a radiant energy density of 600 milliliters.

Although this process is effective, it’s also a time-consuming way to dechlorinate large volumes of water. So you may want to consider installing a filter system that includes a UV lamp, such as the Kind Water Systems UV Water Purifier. It will cost more than the manual process we outlined above but it’ll save you a lot of time and effort.

4. Add Vitamin C

Adding Ascorbic Acid
Adding Ascorbic Acid

Adding one of the two forms of vitamin C—ascorbic acid or sodium ascorbate— to water is an effective and safe method to neutralize chlorine. However, it’s important to measure the amount of vitamin C you put in the water.

As a general guideline, a gram of ascorbic acid can remove 1 mg/L of chlorine per 100 gallons of water. However, this depends on the initial chlorine levels in the water. Once you have the right amount, dissolve the vitamin C in a small amount of water and then mix this water into the entire volume. This should ensure even distribution.

Vitamin C is really cheap, and it has a shelf life of one year when kept in a dry and dark place. So, you can purchase it in large quantities to dechlorinate your water.

5. Add Sodium Metabisulfite

Sodium Metabisulfite
Sodium Metabisulfite

Like ascorbic acid, sodium/potassium metabisulfite is effective at dechlorinating water. It comes in the form of small tablets, and the number of tablets you need depends on the amount of water in your tank. Generally, putting one tablet in 20 gallons of water should take care of the issue.

The tablet will neutralize the chlorine and chloramine before they evaporate. This method works quickly, so it’s used by most breweries and wineries—the byproducts of sodium metabisulfite are harmless and don’t negatively affect the finished beverages.

6. Use a Water Filter

A Water Filter
A Water Filter

Installing a water filter is the most effective way to deal with any contaminant, including chlorine. The two best types of filters for removing chlorine are:

  1. Reverse osmosis (RO) filters: RO filters force water through a semi-permeable membrane with tiny pores. As the water passes through, large particles like chlorine are trapped and water molecules, which are smaller, pass through. RO filters can remove up to 99% of chlorine from water.
  2. Activated carbon filters: These systems contain filters made of activated carbon, which is highly porous and has a large surface area. As water passes through the filter, the activated carbon absorbs chlorine particles. Activated carbon filters can remove up to 95% of chlorine from water.

The main downside of installing an RO or activated carbon filter system is that they tend to be quite expensive. The units themselves are pretty pricey, and you also need to consider the cost of installation and maintenance. However, given their effectiveness, we’d say the price is more than worth it.

If you want to install a water filter to remove chlorine, we recommend the AquaTRU reverse osmosis system.

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Scott Winfield
Scott Winfield
My name is Scott Winfield and researching and writing about water filters and other strategies to purify water has become my full time passion in recent years. I'm glad that you found our site and you can look forward to authoritative and well researched content here to help you get the best in water.
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