Should Reverse Osmosis Water Have 0 TDS?

Should Reverse Osmosis Water Have 0 TDS?

Total Dissolved Solids (TDS) are a combination of minerals, sediments, metals, and salts present in water. People often install RO systems to reduce the concentration level of TDS in their drinking water, but you may be wondering whether RO water should reduce the TDS level to 0. Let’s explore the answer to this question and what the appropriate amount of TDS should be.

Reverse osmosis water should not have 0 TDS. 0 TDS means the water will be void of all the essential minerals such as calcium, potassium, magnesium, and sodium. When these minerals are present in water, they are easily absorbed and beneficial to the human body. 

Total Dissolved Solids contain unharmful minerals like calcium and magnesium but harmful heavy metals like arsenic, lead, and fluoride. RO systems use a semi-permeable membrane to purify water, and almost 98-99% of TDS are removed from water through this process. In this article, we will explore how reverse osmosis systems can reduce TDS and the effects high levels of TDS can have on our health and other areas of life.

Read my comprehensive article about reverse osmosis.

What Level of TDS can RO Systems Remove from Drinking Water?

According to EPA’s regulations on drinking water, an average of 500 ppm TDS is appropriate. Anything that goes above 1000 ppm is dangerous. Let’s take a closer look at TDS levels and their impact:


TDS Level Category Consumption Hazard
<50-30 ppm Low Void of all the essential minerals required by the human body
300-500 ppm Optimal Perfect level of TDS for mineral absorption by the body
500 -1000 ppm Fair Requires filtration and can be harmful for body
1000-1999 ppm Poor Requires lowering by filtration and can be very dangerous for human consumption
>2000 ppm Unsafe Cannot be handled by residential filtration systems and requires proper treatment to lower TDS levels

Learn more about TDS in my article – How Much TDS in Water is Good for Your Health?

RO systems remove all kinds of contaminants from water. They pass the water through a semipermeable membrane with very small pores with pressure. This process reduces the amount of TDS in water to below 25 ppm, which according to the table shared above, is actually below the level required to replenish your body with the necessary minerals.

The optimal level of TDS in water should be 300-500 ppm. This level of TDS contains the right amount of minerals like calcium, sodium, potassium, and magnesium that are required by your body.

A zero TDS will change the pH levels of water and make it extremely alkaline, which is not safe for drinking. So, an appropriate amount of TDS is required in water for it to be healthy for human consumption.

Why Is Checking the TDS Level in Your Water Important?

Water that has been filtered can still have a high level of TDS because levels, after any filtration process, are dependent on the original concentration of TDS in the water source. High levels of TDS can impact the following:

  • The taste and odor of water
  • Your health
  • Quality of the crockery
  • Quality of your skin and hair
  • Structure of your pool or other water bodies in the house

How Can You Check TDS Levels in Your Water?

RO water should have a TDS below 25 ppm. You need to ensure that the TDS levels in your RO water aren’t increasing consistently. TDS levels that keep increasing in your reverse osmosis treated water are an indication that your system needs a clean-up, filter change, or routine maintenance check by an expert.

Here are the different methods through which you can measure the TDS in your RO water:

1. Filter paper and kitchen scale method

This is an old-school method of checking the TDS level in your water, and it utilizes basic kitchen supplies. You will need the following:

  • Kitchen scale
  • Evaporating dish
  • Water beaker
  • Filter paper
  • A pipette
  • Stirring stick
  • 50 ml water sample

Start by weighing the empty evaporating dish and keep the measurement with you for recall purposes later; you can call this measurement X. Pour some water into a water beaker. Use a stirring stick to really mix up the water so all the TDS can be evenly distributed. Take out the water through a pipette and pass it through the filter paper three times till there is some sediment left on the paper. Place the sediments on the evaporating dish for a while until they are dry.

Measure the evaporating dish again and note this measurement, and mark it as Y.

Now use the following formula to measure the TDS level = [(X-Y)*1000]/ml

The final value of the TDS will be measured in the mg/L value.

2. Digital TDS meter

This is actually the easiest way to measure the TDS levels in water. You can easily get a TDS meter at a very reasonable cost and use it to test your water. All you have to do is turn the meter on and immerse it in water till its immersion point and then wait for it to give you a stable reading.

Frequently Asked Questions

1. How is the TDS level in water reduced to zero?

The TDS level in water can be reduced to zero through a process called deionization. This process controls the electric charge of the ions of the elements present in water through ion exchange to completely remove TDS.

2. Can reverse osmosis completely remove TDS from water?

Reverse osmosis systems cannot completely remove TDS from water. They can reduce the levels below 25 ppm. Processes such as distillation and deionization can bring TDS levels down to zero.

3. Can carbon filters reduce TDS from water?

Carbon filters are very effective in removing organic materials from water. However, they cannot reduce or remove sulfates, chlorides, and fluorides etc.

Final Thoughts

Total Dissolved Solids are present in almost every water source, and they should be present in the water at healthy levels. However, a high concentration of these are harmful to human health. RO systems can reduce these to an acceptable level and make the water safe to drink. We hope you found our article useful and can now keep a close eye on the TDS levels in your water.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children.

Recent Posts