Chlorine in shower water - everything you need to know

Table of Contents

  • Where Our Shower Water Comes From
  • Why There is Chlorine In Our Shower Water 
  • The History of Chlorine


It makes up 60% of our bodies. 

Americans drink more than 1 billion glasses of it every day. 

The average American spends 7.8 minutes showering under 15.8 gallons of it. 

Water’s everywhere; but where does it come from? 

The water we shower in, a privilege often taken for granted, comes from lakes, rivers and groundwater. In the US, after water is sourced locally and before it reaches your faucet, it passes through a treatment plant. Here, water undergoes four steps toward purification. 

Coagulation and flocculation kick off the process. This step involves the addition of chemicals to the water for the purpose of binding to dirt and dissolved particles, forming larger particles called floc. Sedimentation does its thing as the floc sinks to the bottom of the tank. The clear water above passes through filters made of gravel, charcoal, and sand, which remove viruses, parasites, and dust. The final step, and why we’re here, is the addition of disinfectant chemicals. Chlorine is added to water to kill germs and bacteria – but see how showering in chlorine, even in small amounts, can harm your skin and hair. In some places, fluorine is added to prevent tooth decay. 

There are geographical quirks that make the US a map of very different drinking waters. Lead pipes, for example, are common in the Midwest and Northeast. These older pipes erode, which can cause levels of  lead to infiltrate the water supply. Water with high salinity, or a saltier taste, is common in Western states. Farming communities face high levels of nitrate in their water due to fertilizer runoff and septic storage. 

Some states take it upon themselves to protect water at its source. Watershed protection measures prioritize conservation and clean water in nature. This is why New York City prides itself as one of the five cities in the country where water doesn’t need to undergo filtration. Water in the city is still subjected to disinfection from chlorine and UV light, with your usual lineup of chemicals to control pH levels and insure against corrosion. 


Here’s how chlorine is used to disinfect our water. The water that comes out of our taps, hoses, and showerheads comes from all sorts of bodies of water, based on where we live. Consulting a Consumer Confidence Reports (CCRs) is the best bet when it comes to understanding the specific process of the water that makes its way to your home. Chlorine’s number one priority is to kill microorganisms that turn to pathogens that can cause waterborne illnesses, though this can have negative impacts on our hair and skin. The efficacy of this process depends on the pH of the water temperature, chlorine level, and the contact time, aka the amount of time chlorine interacts with the water before it’s consumed. 

Chlorine is added to most public drinking water as the last stage before leaving the purification plant and entering our homes. Before chlorine is added, upstream filtration removes sediment that can prevent organisms from chlorine’s full effect. Once water’s in its final stage. Chlorine is added using a feed system that injects the chemical as either a liquid or more commonly, a gas known as gaseous chlorine.

There are some benefits to this chemical, like the almost complete elimination of typhoid and dysentery in the US. But chlorine interacts with many organic compounds negatively, even as a carcinogens at low levels of concentrations, creating trihalomethanes. First introduced in 1908 in Jersey City, New Jersey, disinfecting water through chlorine was used by 64% of public water systems in the US by 1995. Now, chloramine levels up to 4 milligrams per liter (mg/L) are considered safe for drinking water. The chemical is prevalent in 98% of US water filtration processes.


The most common compound of chlorine, sodium chloride, has been around since ancient times. Archaeologists have found evidence of rock salt as early as 3000 B.C. The first human-made compound, hydrochloric acid, was prepared around A.D. 900. First discovered in 1774 by the Swiss-German chemist Carl Wilhelm Scheele, chlorine’s come a long way from its innocent 18th century origin of tinkering in the lab. Just before Scheele’s death, Count Claude-Louis Berthollet, a French textile producer, invented a bleaching agent by dissolving gaseous (non-electrolytic) chlorine in water. 

The chemical element gained enough popularity as a bleach solution to instate the first chemical plant in the US dedicated solely to creating chlorine for bleach in 1892. In the US, the first commercial delivery of liquefied chlorine in cylinders was made in 1909. Less than two decades later, the yearly capacity of all commercial plants rose to 180,000 tons. In 1994, more than 24 billion tons of chlorine were produced. Today, many everyday products contain chlorine or are manufactured through the use of the chemical. Chlorine is among the top ten chemicals produced in the US every year.