Purified Water and TDS Readings

Water, being a universal solvent, can attract a number of other compounds and chemicals. The number of these particles in water is called the Total Dissolved Solids (TDS). However, this is not necessarily a good indicator of the health and safety of your drinking water.  A high TDS reading doesn’t necessarily mean that water quality is poor, as it also reflects the amount of minerals and salts that are present in the water.  

In this article, you will learn about TDS readings.

TDS in Water

Total dissolved solids (TDS) are the amount of organic and inorganic materials such as minerals, metals, and ions. When a soluble encounters water anywhere, it can be washed away together with water. 

Common Sources of Dissolved Solids in Water
  • Natural springs
  • Chemicals treatment for water supply from sewage systems
  • Runoff from road salts
  • Yard chemicals
  • Fertilizers
  • Plumbing at home

TDS are normally mentioned for freshwater systems, since salt consists of some of the ions that make up the definition of TDS. Since TDS is not a primary pollutant, it is instead used as a general indicator of the presence of a broad array of chemical and mineral components in the water.

TDS and pH and Chloride Level of bottled water brand

TDS Measurement

TDS reading gives an easy and accessible way of knowing the basic composition of your water. It became a common water quality tool, too. It uses a measuring device called TDS meter. The Total Dissolved Solids (TDS) is measured as the volume of water with the unit milligrams per liter (mg/L). It is also in the name of parts per million (ppm). 

The normal TDS level ranges from 50ppm to 1,000ppm. According to the EPA secondary drinking water regulations, 500ppm is the recommended maximum amount of TDS for drinking water. If the measurement exceeds 1,000ppm, it is already unsafe. If the TDS reading goes beyond 2,000ppm, a filtration system can not handle this.

TDS Reading Chart

<50-250 ppm

Considered low: missing in some of the minerals that are essential to your health

300-500 ppm

Perfect: This level is the optimal amount for TDS in drinking water

600-900 ppm

Not great: Consider a reverse osmosis system to remove your TDS

1000-2000 ppm

Terrible: Not recommended or safe for use


Worst: A TDS level above 2000 ppm is completely unsafe and household filters can not handle this level of contamination

How to Calculate your TDS
  • Measure the TDS of raw feed water by immersing the TDS tester's probes in a cup or glass of TAP water. Record the results.
  • Measure the TDS of your RO water by filling a cup or glass with RO water (from RO faucet) and immersing the TDS tester's probes in the water. Record the results. 
  • Calculate percent rejection using the following formula:

Example: Tap TDS = 260 ppm RO TDS = 20 ppm Rejection = [(260 - 20) / 260] x 100 = [240/260] x 100 ≈ (.923) x 100 = 92.3

Note: If your RO system is new or the membrane has been replaced, do not test the first tank of RO water. The first tank will contain sanitizer and possibly carbon fines from your new filters that will cause a false reading.

What TDS Does Not Reflect

TDS readings do not reflect the safety of your water. Even when the TDS reading is 0, this water could still contain harmful toxins. Heavy metals, pharmaceuticals, pesticides and VOCs would not be detected in a TDS test. In addition, it won’t also reflect the presence of harmful bacteria, viruses and spores.

What TDS Reading Does Not Mean

Some marketing strategies make use of TDS meters to trick the buyers into believing they need an expensive, state-of-the-art water filter that can filter out or minimize the TDS reading on the meter. In fact, this may not be the case at all. The fact of the matter is that TDS reading is not a true reflection of the quality and safety of the water

If it contains heavy metals and other harmful chemicals, TDS reading is not always a good indicator to buy such an expensive filtration system. Getting a sample of your drinking water tested by a laboratory sounds more an appropriate action before buying any filtration methods. This laboratory test will provide a more accurate range of contaminants and at what levels in your drinking water.

Health Effects of High TDS in Drinking Water

A high level of TDS can affect the taste of your water. But, this may not give immediate harm to your health. In fact, some minerals such as magnesium and calcium may be at high concentration in your water but are beneficial to health. Readings above 500ppm may also require further investigation for toxic particles. Readings over 1,000ppm are completely unsafe for human consumption.

Health Effects of Low TDS in Drinking Water

TDS reading with 0 TDS is not necessarily bad for your health. Low TDS means your water contains fewer solubles, either organic or inorganic chemicals. This low TDS reading may still contain pathogenic bacteria, viruses and cysts. TDS reading can be a good tool to know this number but should also know the source of the water to conclude the quality and nature of your water.

TDS Reading in Purified Drinking Water

The important thing here to note is TDS reading tells you the number or quantity of the amount of dissolved solids in your water. But whether that is high or low, you need to know whether these solids found in your water are safe for consumption.

How to Reduce TDS in Water

A water treatment system helps reduce or remove the TDS in your water. Since a TDS does not tell the type of substances in your water, a water treatment system that can remove a wide range of common contaminants is a good option to consider. First, you may need to know the initial issues in your water, it could be a bad odor or spots on your fixtures. Then, you can determine the right water filter for the types of substances in your water.

Below are three water filters that can reduce the high levels of TDS in tap and drinking water.

1. Reverse osmosis (RO) system

Reverse osmosis system is one of the most efficient filtration systems. This system forces water through a semipermeable membrane that eliminates TDS. It also uses a carbon filter and sediment in the filtration process.

2. Water Distiller

A water distiller removes contaminants through the same process used in nature, evaporation. As the water evaporates, the contaminants are left behind, thereby creating pure water. Rain is a pure water form. This system reflects this process from nature. 

3. Deionization (DI) System

Deionization system removes the total dissolved solids through an ion exchange using resins. These resins are positively and negatively charged called cation and anion. The water produced is highly pure. The DI cartridges and DI systems are called high purity filters. 

Berkey Water Filters

The Black Berkey elements do not take out all of the beneficial minerals. Thus, of the things that a TDS meter will actually detect, the Black Berkey elements will only remove the unwanted heavy metals such as lead and mercury as well as sedimentary minerals such as iron oxide and aluminum. Therefore, your TDS reading will not change much unless you have a significant amount of heavy metals or sedimentary minerals in your water.

The Black Berkey filter uses two elements that could indeed add TDS to any water passing through the elements during its initial break-in (for the first 5 full system flushes). First, all the filters use a type of carbon in their formulation. The carbon fines (not seen under a naked eye) will attach to water as it passes through the element. This is the reason why TDS may increases as it passes through this carbon filter.

Many filters use nano-sized particulates in high-quality carbon micro-fines. It creates an outer “mean porosity” and interior tortuosity of the block or cross-section of the filter elements.

Many tests performed on automated lines ensure the exact porosity. Final destructive tests determine the durability of the element. Two of these tests remove most of these fines. This makes it possible for the water to flow through the element and then through open microspores

In the initial Black Berkey priming, more fines are removed. However, there may still be some non-harmful nanosize carbon micro fines present in the water after the filtration (for the first 5 flushes).

Berkey Water TDS Readings

When the water runs through the Black Berkey element, it may increases the TDS reading. The second and possibly most common reason for increasing TDS is when the Black Berkey element uses the ion exchange media. Ions are a form of TDS and these ions may continue to exist for the life of the filter.

The Black Berkey Filters remove harmful heavy metals but leave behind the beneficial minerals. If you do not have heavy metals in your water, the TDS reading may still increase before and after filtration with the Berkey.

TDS Using Carbon Filters

Carbon filters can remove toxic substances such as VOCs, chlorine and other harmful byproducts in the water. They generally can’t remove the dissolved solids from water. Carbon filters have micron ratings that show how porous the media that makes up the filter cartridge is. 

A micron rating of 0.5 determines the size of the particles it can filter. In this case, it can filter particles as small as 0.5 microns or larger through the filter pores. The solid matter dissolved in water may not be removed from water by filtration. 

What are Carbon Filters

Carbon Filters are like all water filters. They are barriers that capture substances that contaminate your drinking water. In history, Egyptians were the first people who discovered carbon’s detoxifying capabilities. Until now, carbon is used to get rid of the contaminants from the water, making foods and beverages taste and smell better.

How Carbon Filters Work

Carbon filters remove the contaminants by a process called adsorption. Adsorption soaks up the particles like a sponge to water. It adheres to the particles to a surface like iron filings to a magnet. Organic compounds stick to the surface of a carbon filter because water and contaminants are both polar compounds that attract each other.
Carbon filters are especially porous with a large surface area. This makes them efficient at minimizing bad odor, taste and other particles in the water. It acts as huge compartment space for all these contaminants to be trapped as water flows through. The tiny pores are measured in microns. The smaller the micron, the finer the filtration. Low flow rate and pressure give contaminants more time to trap or adhere to the carbon. The more contact time water has with the surface of the carbon filter, the more efficient the filtration.

How to Determine the Performance of Carbon Filters

The first thing to consider the performance of your water filter is to know the types of contaminants present in your water. 
Carbon filters rely on adsorption to remove impurities that give water a bad taste or smell. They have fine micropore size so that even microscopic pathogens and contaminants can be filtered out. If you want to find out that your carbon filter’s efficiency, check whether the smell and odor are to par. The carbon filters are not working efficiently when it has a chlorine aftertaste. If this is the case, it is better to replace the carbon filter cartridge.
Good quality carbon filters are capable not just in removing this chlorine odor and smell, it can also remove a wide range of other contaminants. Such products, such as the Big Berkey filters can remove pathogenic microorganisms, heavy metals and other toxic chemicals undetected in the TDS test.
One important thing to note. When using a carbon filter for removing lead from water, it is important to make regular tests for your water of heavy metals such as lead. This heavy metal won’t likely get detected on a TDS measurement.

Filtration System that Removes TDS

Reverse osmosis and water distillation are two proper water treatments that remove TDS. In the RO system, water is forced through a semipermeable membrane that has tiny pores that are able to prevent dissolved particles from passing through. If you still have high TDS reading after using the RO system, this means you need to replace your filter membranes. Water distillers are also great in removing TDS by transforming the water into gas, this gas turns back into the water. This water is already free from all sorts of impurities and contaminants after cooling. If you have high TDS levels, then the RO system or water distiller may be a suitable option for you. But in most cases, a good quality carbon filter with a fine micron rating is good enough to remove a wide range of contaminants in your water. 


Higher or lower TDS readings do not mean the safety of your drinking water. TDS readings are only a good indicator of the number of particles in your water. 

A quality water purification system should filter out things that are harmful to your body, but leave in the helpful things such as minerals. The Black Berkey elements are designed to leave healthful and beneficial minerals in your water and to extract the unwanted heavy metals such as lead and mercury as well as sedimentary minerals such as iron oxide and aluminum.

A TDS meter does not measure the amount of biological and chemical contaminants.The important thing is to not simply rely on a TDS meter for your measure of whether your water is good.

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