TDS Meter: Levels, Proper Usage, Types, FAQs [Complete Guide]

TDS meter

TDS Meter is a hand-held device to measure the TDS level of water. It is usually battery-operated device that comes with a display screen for showing TDS levels. A TDS meter can determine the TDS within few seconds.

You can also go through the table of contents to read about different aspects of TDS meters.

TDS meter levels

TDS is measure in mg per litre (or PPM). Which gives the weight of impurities in one litre of water. Safe TDS limit is between 150 and 250 ppm.

Below chart explains the different levels of TDS and their importance.

TDS Levels (mg/litre)What it means
Less than 50Very low level. Lacks natural minerals and salts necessary for human body.
50 to 150Acceptable. Decent levels but still may not be sufficient.
150 to 250Healthiest. Best for your heart.
250 to 350Acceptable. Usual range for groundwater in India.
350 to 500Acceptable. As per BIS recommendation.
500 to 1200Not Safe. RO water purifier is recommended.
Above 1200Not Safe. Advanced RO water purifier with multi-stage filtration is recommended.

Now that we have understood different TDS meter levels, let us understand what TDS is and what is its importance.

What is TDS?

According to WHO, TDS represents inorganic salts and small amounts of organic matter present in solution in water. The principal constituents are usually calcium, magnesium, sodium, and potassium cations and carbonate, hydrogencarbonate, chloride, sulfate, and nitrate anions.”

In simple terms, TDS is the amount of dissolved impurities in water. It is measured in ppm or mg/l.

Why is measuring TDS important?

TDS contains essential minerals such as calcium, magnesium, potassium etc. apart from other dissolved impurities. These minerals are important for human body. Therefore water with very low TDS will be devoid of these minerals and is therefore unfit for drinking.

On the other hand, high TDS means high impurities which can harm the body. Also, even high amount of minerals are not good for health. Therefore, some of amount of TDS in drinking water is beneficial.

Unless we measure the TDS levels we cannot decide on the type of water purifier that should be used.

Below chart shows the type of water purifier to be used based on the TDS levels.

TDS LevelMuddy WaterPresence of GermsIdeal Water Purifier
Less than 500 PPMNoYesUV
Less than 500 PPMYesYesUV+UF
Less than 500 PPMNoNoCandle-based
Less than 500 PPMYesNoUF
Above 500 PPMNoNoRO+TDS Controller / Mineralizer
Above 500 PPMYesYesRO+UV+UF+TDS Controller / Mineralizer
Above 500 PPMNoYesRO+UV+TDS
Controller / Mineralizer
Above 500 PPMYesNoRO+UF or
RO+UV+UF TDS Controller / Mineralizer

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Types of TDS meters

Most of the TDS meters come with digital display that shows TDS in PPM (mg/l). A TDS meter can come with standalone TDS indicator or with additional temperature sensor and electrical conductivity indicator (3 in 1 TDS meter).

Standalone TDS meter: It is the cheapest TDS meter available. You will not get any other functionality apart from TDS measurement. This is best for home use, testing TDS of RO water etc.

TDS meter with temperature: These are the most popular type of TDS meters. With added feature of temperature sensors, you can test the temperature of water as well. Also, the price difference between standalone TDS meter and this one is not much, so most of the users prefer to buy these TDS meters.

TDS meter with EC. Usually such meters will also have temperature sensor apart from additional display for showing electrical conductivity. Therefore they are also called 3-in-1 TDS meters. EC is measured in micro Siemens per centimeter (μS/cm). It is mostly useful for research purposes. Therefore you do not necessarily need this type of TDS meter for home use.

How does a TDS meter work?

This device calculates the TDS by measuring the electrical conductivity of water. This measurement of electrical conductivity is commonly used to find TDS. It is based on the assumption that the solids (impurities such as salts and minerals) are mostly ionic in nature and these ions are responsible for electrical conductivity of water. Thus, measuring electrical conductivity gives an idea about the amount of ions or impurities in water.

However, it is not very accurate because some solids such as organic impurities to not conduct electricity therefore the TDS meter cannot measure these impurities.

In any case, TDS meter is the best way to easily find TDS of your home water. And even though the results are not accurate, they are close to actual TDS levels.

How to measure TDS level of water with TDS meter?

TDS meter is a digital device that can be used to find out TDS level of water within minutes. Follow below steps to find out TDS.

  • Take a cup of water with at least 2 to 3 inches depth.
  • Fill it with water sample to be tested and stir it properly.
  • Remove the cap and switch on the TDS meter.
  • Dip the exposed end of the meter into the water for maximum of 2 inches.
  • As soon as it is inserted, the reading on the meter will start fluctuating. It will take few seconds to stabilize.
  • This is the TDS level in ppm or mg/l.
  • If the reading shows x10 symbol then multiply the value with 10 to get TDS level.
  • Take the meter out of water, shake off the remaining water from the meter and place the cap on top of it to secure it.

How to read a TDS meter?

Some TDS meters come with maximum display of 3 digits, therefore, they show reading in PPM will 999 TDS level. For any reading greater than 999, it shows a symbol of ‘x10’, which means that you will have to multiply the reading by 10 to get the TDS in PPM. For example,

  • If TDS meter shows 999 as reading then it means that the TDS is 999 PPM.
  • If it shows 999 with x10 symbol after it then the TDS level is 9990 PPM.

However, many modern TDS meters can show values in PPM even if the TDS is greater than 999.

Care & Maintenance of TDS meter

  • It is important to not to dip the TDS meter electrodes beyond safe limit because the meter is not water-tight and it can damage the digital mater. Usually, damage because of water is not covered in warranty as well.
  • Make sure not to store the device in direct sunlight or in high temperature.
  • Clean the tip (electrodes) after repeated usage.
  • To clean the electrodes, you can soak them in vinegar and then rinse thoroughly with water.
  • For intense cleaning, soak the electrodes in alcohol or bleach. You can rinse it after that.
  • Replace the batteries if they start leaking.

Frequently Asked Questions (FAQs)

Are TDS meters accurate?

TDS meters are not accurate because they measure TDS by measuring electrical conductivity which does not detect certain impurities such as organic impurities. However it is close to actual TDS. Usually actual TDS is plus/minus 2% of TDS value displayed in the device. For example, 100 PPM display will mean that actual TDS is between 98 and 102 PPM.

What is PPM in TDS meter?

PPM (parts per million) is a unit to measure TDS. It is the weight of dissolved impurities (in milligrams) in one litre of water. Therefore it is also represented as mg/l.

How to find TDS of water without a TDS meter?

You can find the TDS in home by using a filter paper and weighing scale. You can filter the water with the help of filter paper and take the weight of deposited sediment on the filter paper. Now divide the total weight (in milligrams) with the volume of water that you filtered. This will give you the TDS of water. Here is the step-by-step method.

Where can I get TDS meter?

Finding a TDS meter shop can be difficult. However, you can buy a TDS meter from e-commerce stores easily in few hundred rupees.

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