Free Chlorination Explained: The Benefits and Possible Downsides

Water utilities supply large amounts of water to customers every day through complex drinking water distribution systems (DWDSs). It’s how most of us get water to drink, cook, shower, do the laundry, and for other household and personal purposes.

Typically, these water providers must take steps to ensure the water flowing to your home meets all state and federal water quality standards. But in most cases, that means treating the water with chlorine and disinfecting their water distribution systems occasionally through a deep-cleaning process called “free chlorination.”

On the surface, free chlorination seems like a no-brainer, considering that a DWDS is a dynamic ecological niche for bacteria, algae, fungi, and other microorganisms (including pathogens). Furthermore, these microbes can be transmitted through the pipe network and cause waterborne diseases in those who consume the water. But despite the incredible benefits free chlorination can provide, we still have to consider the possibility of it leaching chlorine and other potentially toxic contaminants into home water supplies.

That’s why, in this article, we’ll be taking a closer look at free chlorination, exploring topics like, what free chlorination is, how it works, its potential effects on water quality and human health, and how to protect your water supply against any resulting contamination issues.

What is Free Chlorination?

The City of Fort Lauderdale Public Works Department defines free chlorination as “a temporary process that distributes free chlorine in place of combined chlorine (chloramine) throughout the water distribution system as part of routine distribution system maintenance.” It is a standard procedure used by most water utilities across the United States to maintain and protect DWDSs. The process is often performed once every two years or so.

How Does Free Chlorination Work?

Free chlorination is essentially a traditional water-main flushing method using chloramines or chlorine only, the primary disinfectants used in public water systems. Chlorine is a more potent disinfectant than chloramines (made up of chlorine and ammonia) and is usually more effective. However, some water systems switch back and forth between chlorine and chloramines at different times of the year or for other operational reasons.

A few weeks or months before initiating the free chlorination process, cities and Public Water Suppliers (PWSs) issue public notices to inform residents about what streets will be undergoing flushing, the start date, duration, possible disruptions, etc. The procedure can occur in two ways: shock chlorination using the “Slug In” method or shock chlorination by high-pressure metering pump injection, both of which use chlorine. Moreover, they can either be done using conventional flushing or unidirectional flushing (UDF).

In conventional flushing, fire hydrants are opened in different targeted areas and discharge water until accumulations are removed, and the water runs clear. While easy to conduct, this method requires a lot of water and may not clean the pipes properly. With UDF, the water operators isolate each pipeline to create flow in a single direction to clean the pipes quickly. By concentrating the flow, UDF creates higher velocities to clear the pipes. It also requires less water.

Before discussing the two most common free chlorination methods, it’s essential to know the role chlorine plays in the process. When chlorine is added to water, the chemical dissolves and forms radicals that kill pathogens, such as bacteria and viruses. It achieves this by breaking the chemical bonds in their molecules or attacking the cells of the microbes.

That said, here are the two main free chlorination methods used by most water utilities:

● Shock Chlorination Using the “Slug In” Method

This method is often used for large-diameter water mains. It involves introducing a slug or a large amount of chlorine (usually liquid chlorine, calcium hypochlorite granules, and tablets, or sodium hypochlorite solution) into one part of the pipeline being disinfected and moving the highly concentrated chlorine solution in the interior of the pipe with a contact time of at least three hours with the pipe wall with the hopes of adequately sanitizing the downstream sections.

The chlorine tablets are generally used for short extensions of up to 2,500 feet of 12-inch-and-smaller-diameter mains. The number of tablets required is placed on the top of each joint and held in place by a suitable mastic. The main is then filled with water at a velocity of less than one fps (foot per second). Afterward, the water is left in the main to sit for at least 24 hours before flushing.

Next, the operators obtain chlorine residuals to ensure that the required concentration is maintained. This chlorinated water solution should remain in the pipe for at least 24 hours, at the end of which period the chlorine concentration should be at least 25 mg./L. If this is achieved, final flushing can then be accomplished, and chlorine residuals checked to determine that the heavily chlorinated water has been removed from the pipeline.

The “Slug In” method is usually unreliable and does not introduce consistent, evenly-distributed chlorine residuals of 50 to 200 ppm (parts per million) throughout the system. Instead, it allows diluted water with varying residual levels of chlorine to flush through the system. It’s also believed to create very high corrosive chlorine levels (over 500 ppm), damaging fixtures, and corrode copper and stainless steel.

● Shock Chlorination by High-Pressure Metering Pump Injection

Like the “Slug In” method, DWDS operating crews typically use the high-pressure metering pump injection free-chlorination procedure to disinfect pipes and chlorinate water lines. This method involves leaving the water system or pipeline under pressure and using a high-pressure, low-volume metering pump to inject a concentrated chlorine solution as the water flows at a specific flow rate. Once the operators detect a chlorine residual of 50 to 100 ppm at an outlet, they allow the chlorine solution to remain in the pipes for 12 to 24 hours.

Why Free Chlorination?

While free chlorination may seem like a bad practice, mostly due to its chlorine affiliation, it is a vital preventive and maintenance activity that:

  • Allows municipalities to deliver the highest quality water to their customers: Over time, water settles, ages, and becomes affected by biofilm (a thin layer of microbes that grow inside the DWDS). These factors affect the quality and taste of water, so it’s essential to regularly flush and disinfect the mains and hydrants. Thanks to chlorine’s powerful germicidal action, free chlorination can eliminate microbes in miles of water lines, reducing excessive microbial growth inside the DWDSs. Otherwise, this newly-developed uncontrolled microbial community could cause pipe corrosion, nitrification, aesthetic issues (water taste, odor, and discoloration), and health concerns due to pathogens.
  • Helps maintain and protect DWDSs: According to Potomac Local News, this system-wide flush can also help “prevent bacteria from forming a resistance to the routine disinfection treatment process,” which is crucial to maintaining a well-sanitized DWDS and ensuring clean, safe, great-tasting drinking water for public consumption at increased water pressure and flow.
  • Removes mineral and sediment buildup in the water main: Water mains are homes for loose sediment and minerals deposits that build up inside them over time, resulting in discolored water, reduced capacity, and sometimes clogging. Flushing the water mains can wash out the sediment and mineral buildup, improving the water’s color, taste, and odor. Unidirectional flushing at the minimum required velocity can improve the carrying capacity of the mains.

The Potential Effects of Free Chlorination on Water Quality and Public Health

Like all other water main disinfection techniques, free chlorination has its share of disadvantages. Environmental Activist and Water Safety Advocate Erin Brockovich, who gained fame for exposing drinking water contamination that resulted in one of the largest legal settlements ever – $333 million, criticized the practice for being potentially harmful to water quality.

“I am fed up with the barbaric practice of free chlorine burns applied by drinking water utilities that [lose] control of their distribution systems… more so the ridiculous lies they tell!” she wrote in a Facebook post to her 858,315 followers. She also hit out on a bold claim made by water utilities that free chlorination does not affect water quality. She condemned it as “the BIG LIE.” Brockovich suggested free chlorination can result in “toxic levels of trihalomethanes, biofilm, and sludge exposure” and that the sediments and mineral deposits washed from the DWDSs go “right into your homes, water heater tanks, appliances, and drinking water.”

It is indeed a fact that chlorine, chlorine byproducts, sediments, and mineral deposits can have devastating effects on water quality and human health. Let’s go deeper into what you can expect from these types of contaminants in your home’s water supply.

● The introduction of chlorine byproducts in your drinking water

The main problem with free chlorination is that the chlorine naturally reacts with the organic compounds present in the water. Therefore, the chlorine will create disinfection byproducts or DBPs for short. Two of the most toxic DBPs created by chlorine are haloacetic acids (HAAs) and trihalomethanes (THMs).

Research shows that consuming water with HAAs or THMs can lead to several serious health complications, such as stillbirths, bladder and rectal cancer, congenital disabilities, increased risk of kidney and liver cancer. It can also cause problems with the heart, kidneys, liver, and central nervous system.

Inhaling THMs and chlorine can be more dangerous than consuming them because both chemicals convert into vapor at a lower temperature than water. That means taking a shower in chlorinated water can increase your exposure to these toxic chemicals.

And when we think it couldn’t get any worse, a 2005 academic article stated that THMs are more concentrated in the body when absorbed through the skin than drinking tap water that contains the chemicals. These toxic DBPs don’t only affect your health when you drink tap water but might be a significant risk every time you take a shower.

● Bad taste and odor

In a Potomac Local News report, Stafford County said, “some people may notice a slight change in the taste and smell of their tap water” due to the free chlorination procedure. But even at low levels, chlorine in drinking water can impart a foul taste and smell, causing people to opt less for the tap water to hydrate and refresh themselves and go for ice teas, soft drinks, and other sugar-sweetened beverages instead. This decrease in water intake and increase in less healthful choices can cause a host of health issues, such as diabetes, kidney and liver damage, etc. Aside from that, suspended solids washed from DWDSs into your home’s water supply may also affect the taste and smell of your drinking water and the food and beverages you prepare at home.

● Hair and skin issues

Long-term exposure to chlorine can ultimately ruin the quality of your skin and hair. If you shower long enough with chlorinated water, your skin and hair may become dry, itchy, and flaky. Your skin may even turn red when touched, and your hair may feel frizzy and dry. Chlorine can also cause hair color to fade faster than usual if you dye your hair.

Moreover, if you have sensitive or delicate skin or hair, you are particularly vulnerable to the harsh effects of chlorine exposure. This is because the human body naturally produces proteins and oils that form a thin protective coating around your skin and hair.

This layer ensures that your epidermis stays healthy, soft, and well protected. But unfortunately, chlorinated water can wash away this layer and exposure your hair and skin to vicious water contaminants and the elements, causing extreme dryness and irritation.

● Damage to plants and aquatic pets

While chlorine is essential to plant growth, too much can accumulate in leaf tissue, resulting in leaves with a scorched or burned appearance. The leaves may also appear smaller than usual and may yellow and fall off early. Aquatic pets are also vulnerable to chlorine’s corrosiveness, chemically burning marine invertebrates, and fish. In fish, it burns the gills and absorbs through the bloodstream, causing burns throughout the body.

What Can You Do to Prepare for Free Chlorination Flushing?

By now, you may be wondering, “How do I prepare for free chlorination flushing in my neighborhood?” That’s a pretty good question, considering the potential effects free chlorination can have on your water quality and health.

The good news is that installing a quality water filtration system, particularly a whole-house activated carbon filter system fitted with a sediment filter and perhaps a UV purification system add-on, can protect your drinking water against chlorine, chlorine byproducts, sediment, and mineral deposits.

The Springwell CF1 whole-house water filtration system uses high-quality catalytic activated carbon and certified KDF media to remove 99.9% of chlorine, THMs, chloramines, nitrates, haloacetic acids, and many other contaminants from water. It is equipped with Springwell’s ActivFlo technology, which filters water through four powerful stages, including an activated carbon filtration stage. The system filters water using coconut shell filtration media, allowing enough contact time between each filtration stage and the specific pollutants. Adequate contact time is crucial for significantly improving the system’s filtration capacity and performance.

Furthermore, installation and set-up are easy. What’s even better is that it requires little maintenance to upkeep its remarkable performance, and you won’t experience any drop in water pressure while using it. That’s because it has a jaw-dropping flow rate of 9 GPM for a 1 – 3-bathroom unit. If you have a 4 – 6-bathroom unit, the CF4 (the CF1’s bigger sibling) offers a 12-GPM flow rate for steady water flow. But if you have an even bigger space, the CF+ system produces a whopping 20 GPM for a 7+ bathroom unit!

Another impressive feature of the CF1 is that you can connect an optional sediment filter or UV purification system or both to it. The sediment filter removes dirt, sand, silt, debris, rust flakes, and all other suspended solid particles in water the filters’ micron-rated capacity can capture. It also reduces cloudiness in your home’s water supply caused by said suspended solids. On the other hand, the UV purification system is powerful enough to kill 99.9% of harmful pathogens in water, like viruses and bacteria. With this UV add-on, you won’t ever have to worry about nasty germs in your water or getting sick from ingesting them through your drinking water.

If you’re ready to eliminate chlorine, DBPs, sediment, nitrates, etc., from your drinking water due to free chlorination, check out the CF1 4-Stage Whole-House Filtration System or contact us for help finding the best system for your specific needs!

Final Thoughts

Free chlorination is a common practice used by water utilities to maintain and protect drinking water distribution systems from microbial contamination. Using this procedure, they can provide safe, clean drinking water for public consumption. However, free chlorination has a few drawbacks that can make it toxic to your water quality and health without the proper protection. Luckily, the CF1 whole-house filtration system can eliminate contaminants in your drinking water due to free chlorination, producing safe, great-tasting, high-quality water for you and your family.