Categories: all postsWater Facts

Total, Free and Combined Chlorine and Chloride

This can be complicated to understand so we’ve attempted to simplify it here in terms of what you need to understand for the purpose of safe drinking water and water filters.

While chloride is a natural compound in water, chlorine on the other hand is usually added to kill microorganisms in drinking water.

Chlorine

Chlorine in water comes in two basic varieties: Free and Combined.

Simply put

  • Free is the chlorine that is ready to fight bacteria and other microbes
  • Combined is the chlorine that has mixed with organic matter that has mostly been used up
  • Total chlorine is the combination of free and combined chlorine.

Water that is absolutely pure will only have free chlorine as there is nothing to combine with.

The amount of chlorine added depends on how much is required to destroy all organisms in the water systems. Therefore WHO, CDC, EU and other organisations recommend 0.2 to 0.5 mg/l free chlorine to remain once it’s delivered to the tap as this gives a buffer. Sometimes the range is extended to 1 mg/l to ensure safety. The maximum amount of chlorine allowed is 5 mg/l. (read more). For clarity 1 mg/l can also be written as 1 ppm.

Do you want to remove chlorine from tap water? When removing chlorine it’s the free chlorine we want to reduce as this causes the by-products as well as potentially poor smell and taste. The combined chlorine is much more difficult to remove as it won’t be adsorbed by activated carbon.

To measure the free chlorine in your tap you can use simple test strips. This also allows testing of tap water before and after filtering to see the results. See for example SenSafe.

Activated carbon filters such as TAPP 2 remove more than 95% of the free chlorine.

However the chlorine removal may differ depending on water pressure, temperature and pH. Therefore we’ve limited TAPP to about 2-4 litres of water minute.

Chloride

Chloride (Cl-1) is a natural compound in drinking water where the amount depends on the source. It’s generally combined with calcium, magnesium, or sodium. Some places have less than 10mg/l while others have considerably higher amounts around 250mg/l. Sea water contains over 30,000 mg/l as NaC1. The recommended maximum allowed in tap water is 200-250mg/l.

Read more from WHO.

Chloride in water may be considerably increased by treatment processes in which chlorine is used. It’s also associated with leaching/corrosion from piping.

Activated Carbon filters such as TAPP 2 typically removes between 70-90% of the chloride.

Other information

If you want to learn more about chlorine and chloride and how to remove them from tap water read these other blogs

Read more about how to remove chlorine and chloramine from tap water.

Read more about what TAPP 2 removes.

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Magnus

Computer geek and entrepreneur. Spent the last 5 years learning everything about tap water, water filters, bottled water and everything else you can imagine. Believes in radical transparency and writes a lot about myths and surprising facts. Drinks a lot of tap water, usually filtered.

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