How To Measure TDS In Water [ TDS Meter]


Before you are shopping around for a water purifier, the first thing that you should check is the normal TDS level of the water that you are getting at your home.

You might be getting the drinking water from direct natural sources ( Bore water) or processed water from the water board, but you should always check the TDS level of drinking water before drinking it.

But what is TDS? How do we measure the TDS and what is the acceptable range of TDS in drinking water? We will answer all these questions and will show you how to measure TDS in water in this article.

What Is TDS Level?

Whether you are getting water directly from the ground or your water board is processing it, there would be some impurities in the water, no matter what you do.

For example, the water board is processing your water and makes it pure. But while piping it to your home, the water may collect some impurities from the pipe surfaces. Right?

So 100% purified water is a big challenge and not possible.

In fact, some degrees of impurities are required to make the water tasty. Some minerals that are there in the form of TDS are essential for our bodies.

Generally, drinking water consists of two types of impurities, Organic and inorganic impurities. Sodium, potassium, magnesium, and calcium are some of the inorganic substances. Salts are organic contaminants.

The groundwater can also have some metals like lead, mercury, and arsenic which are not good for our health and should be filtered out. These are considered slow poisons in the water.

The full form of TDS is Totally Dissolved Solids. What that means is the amount of unwanted solids that are dissolved in the water is called the TDS in water.

As I already said, not all solids that are dissolved in water are bad for our health. Some solids are good for our health and make water tasty too.

That is why there is no definite best TDS level of drinking water. If the water has good substances, then the water is good, even if the TDS level is more.

The TDS in water is measured in milligrams per liter ( mg / L).

Is TDS Necessary?

If the water does not have any TDS, then it will be tasteless. Salts like calcium, magnesium, and potassium make the water tasty and add flavor. So we should not remove all the TDS from the water.

0% TDS water is not good for your health too. That is why many water purifiers come with a TDS controller to add back the required minerals that were removed in the RO process. Minerals are a must for our bodies.

What is the allowable TDS level for drinking water?

As per the United States Environment Protection Agency ( EPA), the TDS level of 500 mg/l is considered to be safe if the percentage of other contaminants is within the range shown. The 500 mg/l thresholds may vary in different countries.

tds in water
Source: EPA

In India, as per the Bureau of Indian Standards (BIS), the allowable TDS level for drinking water is 500 mg/l. But if no better water source is available, a TDS level of more than 500 mg/l is also acceptable if the substances are not harmful to our health.

Here is the chart showing the permissible and maximum limits of different substances that are usually dissolved into drinking water in India

tds in water

TDS In Water: Acceptability Levels

As already mentioned that BIS allows TDS level for drinking water up to 500 mg/l and it can go up to 2000 mg/l considering the fact that the proportion of harmful substances is within the range.

The below table shows the allowable TDS level and the justification for that allowable TDS limit.

TDS Level ( Mg/LReasons for Acceptability/Non-Acceptability
<50Not Acceptable->Does not suitable for drinking as <50 TDS level does not carry any taste or flavor
>50<150Acceptable-> It is acceptable as it is due to minor industrial contamination
>150<250Acceptable->BIS considers this TDS level is excellent for cardiovascular health
>250<350Acceptable-> Groundwater/borewell water has this TDS range. It is quite acceptable unless it does not contain any harmful chemical
>350<500Fair-> TDS level of 500 mg/l is the maximum range. Beyond that range, the water is NOT suitable for drinking
>500<1200Not Acceptable-> Though anything above 500 mg/l of TDS is not acceptable for drinking water, you can use water purifiers to bring the TDS down to at least 500 mg/l. If you can then it can be used for drinking
>1200Not Acceptable-> Even RO water purifiers can not bring the TDS level down to 500 from 1200. That is why if the TDS level is more than 1200 mg/l then the water is unhealthy for consumption

TDS In Water: Palatability Levels

The palatability levels and acceptance level is quite different. The acceptance level is what the regularity authority has mandated. The palatability level is what the general consumer decides.

TDS Level ( Mg/LPalatability Quotient
<300Excellent for drinking
>300<500Acceptable but not excellent for drinking
>500<900Not acceptable but if you can lower the TDS by using a water purifier, then it’s fine
>900<1200Not acceptable and water purifiers also may not be able to reduce the TDS level to the acceptance level
>1200Not acceptable at all

How To Measure TDS In Water [ TDS Meter]

Now that we know what is TDS in water and why we need to reduce the TDS level, let us learn how you can measure TDS in water.

See, there are many methods to measure TDS in water, but the best method is using a TDS meter. You can easily get it from a local shop for Rs 100-200. You can also order it online from Amazon.

Digital TDS meters are very precise compared to other manual methods. The measurement range is between 0 to 5000 PPM

Digital TDS meters are the best and simple to measure TDS in water. You don’t need any other equipment and you don’t need to do any calculations.

How to Measure TDS in water using a digital TDS meter

TDS meter
Digital TDS Meter
How to measure TDS in water
Here are some of the common steps that you need to follow to measure TDS in water.
Remove the protective cover
There is a protective cover in the digital TDS meter that you need to remove first. The portion under the protective cover is the area that you need to immerse.
Set the mode to TDS
Usually, there are two modes, one is the temperature and the other is the TDS. Since you are measuring TDS, you need to switch to TDS mode
Immerse the TDS meter
You only need to immerse the marked area of the TDS meter into the water. Please keep in mind that the whole TDS meter is not waterproof. So you only need to immerse the area that is marked.

Please make sure that you are not dipping the whole TDS meter in the water and also you should not expose it to direct sunlight.
Keep the TDS meter immersed for about 30 seconds
30 seconds is usually enough for a digital TDS meter to calculate the TDS level in the water.
Press the HOLD button and take out the TDS meter
Yes, it’s very important to press the HOLD button so that the TDS meter keeps the current reading intact.
Observe the reading
Now it’s time to look at the reading. Some TDS meter shows the value in x10 format. So in that case, you need to multiply the reading to get the actual TDS level in the water.

Here is one video that might be helpful in understanding how to measure TDS in water

How to reduce the TDS in water?

Now the big question is, how to reduce the TDS in water so that it is safe for drinking. There are many methods available. But below three methods are very common for general use.

Distillation
Reverse Osmosis
Deionization

Distillation

Distillation is the process of boiling water until it evaporates and then condensing it leaving behind impurities at different boiling points.

Distillation is an effective process to remove harmful bacteria, heavy metals, and chemicals from water.

Reverse Osmosis

The full form of RO is reverse osmosis. Almost all water purifiers nowadays use RO technology in addition to UF and UV technology.

RO is a water filtration process in which water passes through different semi-permeable membranes. TDS impurities are generally greater than. 0001 microns sizes. So those impurities get stuck in the filter and pure water passes through those filters easily.

how ro purifier works

RO technology is often combined with UF ( Ultrafiltration ) and UV ( Ultra Violet ) technology to purify the water. UF technology is basically an ultrafiltration technology and UV technology is basically for killing germs in water using ultraviolet rays.

If you want to get 100% pure water, then I would suggest you go with a water purifier with RO+UV+ UF technology. You can learn more about these techniques in this article.

Deionization

Deionization is the process of removing positively and negatively charged ions from the water by passing them through electrodes. The resultant water is pure water. However, this process is not effective in removing all TDS.

Frequently Asked Questions ( FAQ)

What Is TDS In Water

The full form of TDS is Totally Dissolve Solid. So TDS in water means the number of solids that are dissolved into the water.

What is the acceptable TDS level for drinking water

A TDS level of below 500 mg/ l is considered the acceptable TDS level for drinking water. However if the TDS level is less than 300 mg/l, then its excellent for drinking

What is the usual TDS meter price?

TDS meters are priced around Rs 100-200. However, you may get better deals on Amazon


Rajib

Rajib

Rajib is the Co-Founder and the Lead Product Analyst of RiansTech. A BTech in Mechanical Engineering and a veteran in the Home Appliance industry with over 17 years of experience in designing appliances for industry leaders like GE and Whirlpool. He also runs a successful niche blog (RiansClub) on Mechanical Engineering

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