How to Increase TDS Levels in RO Water

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Reverse osmosis water has very low TDS levels by default.

While that’s the desired effect for most people, sometimes you may want to take things in the opposite direction a little bit.

Increasing the TDS of your reverse osmosis water can make sense in some cases, especially when it comes to personal preferences like taste.

How to increase TDS levels in RO water? Let’s discuss!

Key Takeaways

There are several ways to increase the TDS levels of reverse osmosis water:

  • Remineralization – this is by far the best way
  • Increasing the TDS of the feed water
  • Using a TDS controller
  • Changing the pressure and/or temperature of the input water

How to Increase TDS Levels in RO Water

So, how can you increase RO water TDS?

There are several ways to increase the TDS level of reverse osmosis water. Most of those are easily accessible, so you should have no problem implementing them in your situation.


Remineralizing your RO filtered water is the best way to increase its TDS levels, as it also comes with various health benefits thanks to the increased consumption of minerals.

3 Ways to Remineralize RO Water

  1. Remineralization filter: A remineralization filter is often used with reverse osmosis systems by people concerned about the decreased mineral content of the filtered water. These filters work by adding various beneficial minerals to water as it passes through them. Naturally, this also increases the TDS level. A remineralization filter is perhaps the most straightforward way to increase the TDS of your RO water.
  2. Mineral drops: You can also purchase mineral drops in small bottles. Simply add a few drops to the RO water before drinking it, and that’s it! It can seem a little inconvenient at first, but it has the advantage of allowing you to more precisely control how many minerals you’re consuming.
  3. Alkaline water pitcher: There are water pitchers specifically designed to increase the pH of water by adding minerals to it. This accomplishes more or less the same effect as the above methods, but in a more convenient package that you can easily move around.

woman with water filter pitcher

Increase Feed Water TDS

Theoretically, you could also increase the TDS of your reverse osmosis water by increasing it at the source. Since reverse osmosis reduces TDS by a certain percentage, usually somewhere around 80 to 99%, increasing the number of dissolved solids in your input water will proportionally increase the TDS level of the output water as well.

However, this doesn’t make much sense for a number of reasons. First, you’ll have to use more resources to increase the TDS level of the feed water, as most of them will get stripped away by the reverse osmosis process. Second, this will put extra strain on your RO membrane. It’s better to simply add minerals as a post-filtration stage instead.

Use a TDS Controller

A TDS controller is a device designed to increase the TDS levels of filtered water. It has two inputs and one output. It works in the following way: The input water stream is split into two parts, A and B. Line A is fed into the reverse osmosis system as usual. Line B goes into one input port of the TDS controller without being filtered. The filtered (output) line of the reverse osmosis filter is connected to the other input port of the TDS controller. Internally, the controller mixes the two streams in a fixed proportion, increasing the TDS levels of the output water.

You may have noticed an obvious problem in this setup: You’re mixing unfiltered water with your filtered reverse osmosis water. This carries the risk of reintroducing some contaminants. In some setups, the unfiltered water line (B) is passed through a UV filter before it enters the TDS controller. While this does neutralize microorganisms, it does nothing against other types of contaminants like heavy metals.

Reduce Feed Water Pressure

Reducing the pressure of your feed water line will increase the TDS levels of your RO filtered water. However, it will also result in more water going to waste due to the way a reverse osmosis system works. In addition, you will notice a decline in the quality of your filtered water, as some contaminants will make their way into it – not a good method!

Increase Feed Water Temperature

Higher feed water temperatures are associated with a decreased salt rejection rate. And while that’s certainly one way to increase your TDS levels, it’s far from optimal. It causes the membrane to expand, allowing some contaminants to potentially pass through, and possibly decreasing the lifespan of the membrane due to the constant shrinking and expanding.

Why Increase TDS Levels in RO Water?

But why would you want to increase the TDS levels of your reverse osmosis water in the first place? The whole point of reverse osmosis is to bring those levels down, right?

There are several good reasons for this.

  • One has to do with corrosion – reverse osmosis water is much harsher on your plumbing and appliances, so increasing its TDS levels can mitigate that effect somewhat. This is particularly important when applying reverse osmosis at the point of entry.
  • Some people also don’t enjoy the taste of reverse osmosis water, because it’s noticeably flatter than regular unfiltered water. Simply put, TDS adds flavor.

What TDS Level in Reverse Osmosis Water Is Right?

The ideal TDS level of reverse osmosis water is somewhere between 10 and 50. While going above 50 is still okay in terms of drinking water quality – up to around 300, in fact – it could indicate problems with the operation of your reverse osmosis system. That’s why it’s recommended to regularly test your system to ensure its optimal performance.

If you have any questions about increasing TDS in RO water please don’t hesitate to leave a comment below!

About the Author Gene Fitzgerald

Gene Fitzgerald is one of the founders of BOS and currently head of content creation. She has 8+ years of experience as a water treatment specialist under her belt making her our senior scientist. Outside of BOS, Gene loves reading books on philosophy & social issues, making music, and hiking.
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