Can Water softeners lower the TDS or Total dissolved solids of water?

Does water softener lower TDS or total dissolved solids from water?

Nowadays, water softeners are essential utensils for most households. That’s because we get hard water in more than 85% of regions in the US. 

In addition to the hardness of water, another parameter is vital to detect the water quality. And that is the volume of total dissolved solids in the water, in short, the TDS of water.

Many of us tend to confound the hardness of water with the TDS value. But, there are some definite differences between the two. 

In this post, we’ll be discussing the TDS value of water and whether water softeners can affect the TDS value. And, as for us: Aquaseep gives you solutions to your day-to-day household activities mostly centered around water. Check out more about us on our blog page here.

Now, find out about water softeners and TDS. Let’s go.

What is TDS?

The parameter TDS stands for total dissolved solids. It works as a quantitative measurement of the impurities dissolved in a liquid, particularly water.

In general, most of us get our water through the municipal water supply. The supplied water gets collected from natural reservoirs. Naturally, this water carries tons of dust, rust, sediment, and other dissolved minerals and pollutants.

Then, the collected water goes through an extensive water treatment process. As a result, the resultant water won’t contain most of the pollutants. But, the dissolved minerals continue to persist in the water.

And, therefore, the water we get every day contains a significant amount of dissolved molecules. The minerals include Calcium, Magnesium, Sodium, Iron, and other ions. 

The TDS measures the total quantity of dissolved solids in the water. Hence, it not only gauges the density of only Sodium or Calcium ions. Instead, it estimates the cumulative concentration of all the different types of dissolved molecules in the water.

The unit of TDS is usually mg/L or ppm. For example, if one liter of water contains 50 mg of Calcium ions, 60 mg of Magnesium ions, and 100 mg of other dissolved ions, its TDS value is 210 mg/L.

The TDS value also works to quantify water quality. According to WHO, water with TDS between 300 to 600 mg/L is considered excellent. Here is a table showing you the relationship between water quality and TDS

TDS level

Water Quality

Recommended action

Less than 50 mg/L

Bitter taste

You should invest in an alkaline filter

Within 50-300 mg/L


No action needed

Within 300-600 mg/L


No action needed

Within 600-900 mg/L


You can buy a simple Carbon block filter to keep the TDS level in check

Within 900-1200 mg/L


You should buy a RO filter

Over 1200 mg/L


You need to invest in a robust Reverse Osmosis water filter

If you would like to find out more about TDS or total dissolved solids, you should check out our post here. You can also visit our page here to learn about how water treatment plants work.

How does a water softener work?

Water softeners use ion exchange to reduce the hardness of the water. In this process, ions like Calcium, Magnesium, Iron, or Manganese get exchanged with Sodium ions. As a result, the water gets soft.

The ion exchange mechanism gets facilitated by the resin beads inside water softeners. Crosslinking between divinylbenzene and styrene forms the resin polymer.

Then, it bonds with anionic functional groups to contain Na+ ions. And, these Na+ ions hold the key to water softening. By definition, hard water consists of more than usual Calcium and Magnesium ions.

As the Ca2+ and Mg2+ ions pass by the resin beads, they replace the Na+ ions. The replacement occurs as there are fewer ion exchange centers than the number of ions.

Being the majority, the Ca2+ and Mg2+ ions can replace the Na+ ions. On this note, the Ca2+ and Mg2+ ions are bi-valent while the Na2+ ions are monovalent.

Therefore, every Ca2+ or Mg2+ ion would replace two Na+ ions from the polymer chain. The replaced Na+ ions dissolve into the water while the Ca2+ and Mg2+ ions form stronger bonds.

And in this way, the hardness ions- Ca2+ and Mg2+ get trapped in the resin beads. As more and more Calcium and Magnesium ions get replaced, the product water gets softer and softer.

Also, the resin beads need regeneration as more and more Ca2+ and Mg2+ ions accumulate. It happens by passing through a brine solution with water-softener salt into the resin beads. 

The brine solution with plenty of Na+ ions forcibly replaces the Ca2+ and Mg2+ ions. The ions then get flushed out, and the resin beads get fresh to work again.

Can water softeners lower the TDS value of water?

As a water softener exchanges one Calcium or Magnesium ion with two Sodium ions, it releases more dissolved solids into the water. Eventually, it leads to higher values of TDS.

In the previous section, we showed you how a water softener works. The resin beads come with a multitude of ion-exchange centers. There, the Ca2+ and Mg2+ ions bond with the polymer.

And, in the process, the Na+ ions get released. To maintain the balance of electrical charges in the resin, one Ca2+ gets replaced with two Na+ ions. The same goes for Magnesium ions as well.

So, you see, the number of ions increases as it goes through water softeners. And, therefore, the TDS level also goes up accordingly.

But, as the water loses a significant portion of the Calcium and Magnesium ions, the hardness of water will go down. As a result, the water becomes suitable for washing and doesn’t cause limescale build-up inside the tubes, water heaters, etc. 

So, in a nutshell, the water softeners will increase the TDS of water while reducing hardness.


Throughout this post, we discussed how water softeners work and increase the TDS of water. Therefore, you can see, there is no direct correlation between hardness and TDS.

High TDS water can be soft if it doesn’t contain many Calcium and Magnesium ions. And, the product water from water softener falls into this category.

If you would like to reduce the TDS of water, you should invest in a reverse osmosis water filter or a water distiller. If you’re looking for a tankless RO water filter, you should check out our post here.

Also, if you would like to invest in a water softener, you should check out our post here. We hope we’ve been able to answer all your queries on water softeners and TDS.

If you still have some questions left, you can leave those in our comment section. Also, if you would like to read more informative posts like this, you should check out our blog page here. Cheers!!!

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