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All About TDS (Total Dissolved Solids)

The below is a compilation of answers recieved to TDS related questions on India Water Portal. Contributors include:

Mr. S.S. Ranganathan

Dr. Jagadiswara Rao

Prof. Shivaji Rao

Mr. Taral Kumar

Mr. Chetan Pandit

Our thanks to all the respondents -- IWP


 1.) What is TDS ?

TDS is Total Dissolved Solids.

Water dissolves the minerals present in the strata of soil it filers through in the case of ground water and, in the case of surface water, the minerals present in the soil over which it flows (rivers/streams) or over which it stands (lakes, ponds, reservoirs).The dissolved minerals in water are commonly referred to as Total Dissolved Solids (TDS). The TDS content of any water is expressed in milligrams /litre (mg/l) or in parts per million (ppm). These units are equivalent.
The minerals are basically compounds (salts) of Calcium(Ca), Magnesium(Mg) and Sodium(Na) What is commonly called as ‘hardness in water’ is due to the compounds/salts of   Ca and Mg such as  Calcium or Magnesium Chloride, Calcium or Magnesium Sulphate ( CaSo4, MgCl, etc).Some types of dissolved solids are specifically dangerous even in low quantities. This includes arsenic, fluorides and nitrates. There are particular standards for the acceptable amounts of these elements in water and in some cases like fluoride, there is some disagreement as to what constitutes safe levels.

 Leaving aside the specific harmful chemicals fluoride and arsenic, drinking water for human beings should contain some level of minerals (TDS), but these levels should not be excessive.

2.) What are the TDS standards ?

The standard that applies to India is the BIS 10500-1991 standard.This standard used the WHO standard as the basis and has been amended subsequently to take into account the fact that over exploitation of ground water which has the largest share of water supplied for human use has deteriorated to such an extent that the crucial parameters such as TDS, hardness, Chlorides, etc usually exceed the desirable levels substantially. Consequently, a higher permissible limit has been specified. Water used for drinking becomes unpalatable when the TDS level is above 500 mg/l, but lack of any better source enables people consuming such water to get used to its taste. The BIS standard applies to the purity level acceptable for human beings to drink. For practically all industrial and some commercial uses, the purity levels required are very much higher and in most cases demand water with virtually no residual dissolved solids at all.   

BIS Standard says that the maximum desirable TDS is 500 mg/L and the maximum permissible level in the absence of a better source of water is 2000 mg/L. A related standard is the 'hardness measured as CaCO3" where the maximum desirable is 300 mg/L and maximum permissible is 600 mg/L.

Click here for reference

WHO Standards:

"Water containing TDS concentrations below 1000 mg/litre is usually acceptable to
consumers, although acceptability may vary according to circumstances. However, the presence of high levels of TDS in water may be objectionable to consumers owing to the resulting taste and to excessive scaling in water pipes, heaters, boilers, and household
appliances (see also the section on Hardness).
Water with extremely low concentrations of TDS may also be unacceptable to consumers because of its flat, insipid taste; it is also often corrosive to water-supply systems "
Reference: [url][/url] 

US EPA Standard: The U.S. Environmental Protection Agency (EPA) recognises broadly two categories of drinking water standards, known as maximum-contaminant-level goal (MCLG) and secondary maximum contaminant level (SMCL). The MCLG is a health goal set at a concentration at which no adverse health effects are expected to occur and the margins of safety are judged “adequate,” while the SMCL is a non-enforceable guideline that presents no risk to human health. While fixing no limit for MCLG, the EPA has fixed an upper limit of 500 mg/L for SMCL. This limit has been fixed to avoid undesirable aesthetic effects of odour, taste and colour that could be felt by consumers and technical effects of corrosion, incrustation, staining, scaling and sedimentation of pipelines and other fixtures that convey water. Despite not fixing a limit to MCLG of TDS, high TDS water can have certain other constituents at harmful levels of SMCL to cause adverse health effects. Thus MCLG can be a few times more than the SMCL.

Very low TDS: Due to insipid or bitter taste and lack of useful minerals, too-low TDS also causes problems. There does not seem to be a generally accepted lower limit, but 80 mg/L may be used.

3.) Measurement:

TDS can be measured very fast using a low-cost portable conductivity meter (TDS meter) calibrated to give TDS directly by anybody with extreme ease. It costs hardly Rs. 2000/- and the only recurring expenditure is occasional replacement of batteries. It is worthwhile for users of well water, piped water and packaged water and practitioners of rainwater harvesting and groundwater recharging to test water TDS as a matter of routine. It may be noted that TDS of rainwater is only a few tens of mg/L. Any sudden increase in TDS of water is a signal that water is getting contaminated with some high-TDS water.

 4.) Mitigation

UV, UF and other conventional filtration methods will not affect TDS. The only one which works is Reverse Osmosis

Reverse Osmosis:

RO is the only commonly used domestic filtration system that removes even the dissolved impurities. RO is required if the Total Dissolved Solids (TDS) exceeds a certain value. (what is the upper limit ? Look for discussion on that elsewhere in IWP). RO is also suggested if you have reasons to believe that your water may be contaminated with sewage/ pesticides/ heavy metals/ industrial effluents.

A problem with RO is, it needs a lot of water. It divides the input water in two parts, and forces the dissolved solids out from one part in to other. Thus, the output comprises two streams of water – a “clean” stream with low TDS and cleaned of other impurities too. And a “reject” stream that is even more dirty than the input water. Typically, an input of 3 liters will give 1 liter of clean water and 2 liters of “reject”. Theoretically, the “reject” water can be used for mopping the floor etc. but few have the discipline to do that.

Reduction of TDS changes the taste and pH of water, and it is not good to reduce the TDS too low. Some manufacturers make a hybrid machine that combines RO with either UV or UF. Bulk of the water is processed by RO, to remove dissolved solids; and some is processed by either UF or UV, to kill micro-organisms, but retaining the dissolved solids. The two are combined to restore the dissolved solids to some lower limit. The ratio of mixing the two can be controlled by user.

The cost of RO systems is in the region of Rs. 10,000/- to 15,000/- The RO works under some pressure, which is developed by an internal pump, and therefore it needs electricity to operate.

With very high TDS levels in the 1000s, conventional domestic RO units may not be able to work

Rainwater harvesting is a useful permanent solution where other sources of water have unacceptably high levels of TDS or hardness. TDS of rainwater is a few tens of mg/L

Water softening does not reduce TDS. In water softening sodium replaces calcium and magnesium, in the dissolved solids which causes a minor reduction only in TDS.



51. You should use Blucol R.O

You should use Blucol R.O systems the quality and services are best

52. TDS level is 110 - What purifier should I buy?

The TDS level while checking was 110. What kind of purifier should I buy, please suggest.

53. How to reduce high TDS levels of borewell water at Chennai?

Dear Sirs,

The TDS level of my borewell water at Chennai is 10600 ppm. The depth of the borewell is 58ft. I would like to reduce the TDS level to around 4000 ppm. I cannot install a domestic-RO-plant (or) dig another borewell of a lesser depth. Both are very expensive.

Kindly suggest some other indigenous methods for the same.


54. Which water purifier is good for a TDS of 350?

I live in Gurgaon and here TDS level is 350. Which purifier is good for us?

55. Make sure you filter the water and disinfect with UV

Dear Mr. Suneel,

Please go through the following comments from users on the subject.

The safe limit is 500 ppm for TDS. Make sure your water is treated with a filter and disinfectant using  UV. RO is not a must for you. -

If your feed water has TDS of only 350, why do you even need to do a RO on it and reduce the TDS to 4? Water with 350 TDS will taste better than water with TDS 4. The presence of some salts in the water actually makes water more palatable. -

Seetha Gopalakrishnan
India Water Portal Team

56. Why the water purifier plant is designed to reduce conductivity?

Can any body tell me why the water purifier plant is designed to reduce conductivity and produce ultra-pure water in water electrolysis plant as water is a good conductor of electricity?



57. Purified to remove salts which contribute to its conductivity

Water is purified not to reduce its conductivity but the conductivity of the salts in it which contribute to its conductivity. Water with a lot of dissolved salts is not palatable and some salts may also be harmful to the body. Ultra pure water is used for certain specific purposes and not for drinking or cooking.

Indukanth Ragade

58. A 50 PPM and 100 PPM in water is premisible

Ultra pure water is the one which has conductivity below .4 milisimens.

This water is used in electroplating industry.  The conductivity and TDS  have little corelation.

By using Lancet equation i.e. TDS ×0.2 mili= conductivity, we should have optimization for our drinking water. A 50 PPM and 100 PPM is premisible.

Zarna water technology

59. Contradictory statements provided

This is with reference to the note of ZWT under the above title "A 50 ppm and 100 ppm is permissible" dated 21st Dec 2012, where it is stated that the conductivity of water is not connnected to the quantum of salts in it.

This is contradicted by ZWT itself when the equation quoted to obtain the conductivity of water (Lancet Equation) which is itself based on the TDS! One does not also see what is the relevance of the information on ultra pure water.

Indukanth Ragade

60. TDS treatment facility request

I have been retained by a client to research companies that could potentially handle waste water from drilling.

As you may know, much of the waste water is the byproduct of a drilling process called hydraulic fracturing, or fracturing, which pumps at least a million gallons of water per well deep into the earth to break layers of rock and release gas. When the water is sucked back out, it contains natural toxins dredged up during drilling, including cadmium and benzene, which both carry cancer risks. It can also contain small amounts of chemicals added to enhance drilling. State DEP (Department of Environmental Protection) officials say one of the most worrisome contaminants in the waste water is a gritty substance called Total Dissolved Solids, or TDS, which you address here on your forum. Drilling waste water contains so much TDS that it can be five times as salty as sea water as you are well aware and has been raising havoc with surrounding streams and plant equipment. Large quantities of TDS has been clogging machinery and affecting the color, taste and odor of drinking water – precisely the problems reported on this page. While TDS isn’t considered particularly harmful to people, it can damage freshwater streams, which is what happened when TDS levels spiked in a surrounding creek this month.

West Virginia’s DEP is investigating whether TDS-laden waste water from a coal mine near the creek could be to blame. It is also investigating reports that waste water from natural gas wells may have been illegally dumped into the stream. Gas drilling companies have been currently disposing of their waste water in municipal sewage plants and in some industrial treatment plants, which then discharge it into rivers and streams. The U.S. Environmental Protection Agency warns against this form of treatment, because the plants aren’t equipped to remove TDS or any of the chemicals the water may contain. Of even more concern, TDS can disrupt the plants’ treatment of ordinary sewage, including human waste. Can you recommend a large scale operation plant, or system that can handle this massive quantity of waste water economically? Could I expect to serve as a mediator for your company and it's product line to the end user in the United States? I am located about 125 miles from my client (end user) in the US. Please advise to the best path to solving this waste water problem and thank you for your anticipated reply.

Randy Zimmerman Zimmerman and Associates

61. TDS in drinking water

Lot of confusion is being seen on TDS.Can someone really come out with real level of TDS as suitable for the Human Consumption. Look forward to your reply.

62. 100 PPM in water is the permissible limit for drinking

Water with 10o PPM is the permissible limit for drinking

63. Minimum TDS required in drinking water

Dear sir,

I want to know what is the minimum desired level of TDS for health, I am using RO water having 10 TDS is it safe for health?

Thanking you

Pradeep Tyagi

64. Should I use RO or UV, 108 is TDS level in drinking water


TDS level of drinking water of my borewell is 108. Should I use RO or UV with any other safety measures? All venders says their product is the best. Please let me know.


65. Your water is of excellent quality - No need for RO or UV

Dear Mr.Dash

Your borewell water is of excellent quality and can be safely drunk after being boiled and cooled. There is absolutely no need for RO or UV or any other system. Don't waste money and don't fall for the salesmen's talk. Th ideal limit for TDS is upto 500.

Indukanth Ragade

66. What is impurity of drinking water?


What is impurity of drinking water?

67. TDS level 475, should I continue to use UV or RO system?

Dear Sir,

I have recently shifted to Gurgaon and got my UV water purifier installed. Here the TDS level is 475 at my place.

Kindly advise whether if I should continue to use the same UV system or should I go for RO system?


68. Use RO purifier with TDS controller

You are having UV filter and that is ok to kill bacteria. The TDS level in the water is above permissible limit and you feel that taste is sour.

Then use RO purifier and essure that it has a TDS controller. 

In market all filter will have TDS controller, but just ask as you have TDS 400 and it may reach to 5PPM or so and there is need to regulate it with a controller.

69. Drinking water has no taste with 403 TDS-Which purifier is best?


Our borewell water has a TDS of 403.  There is no taste in the water, so I am planning to buy water purifier. Please suggest which water purifier is good for this TDS level. As per the reviews upto 500 Mg/L is fine to drink. Though the borewell water which I am using has a TDS of 403, there is no taste in it.

70. TDS is 10 after using RO - What should we do?

Dear Sir,

Previously, TDS level of our drinking water was 300. We used a RO filter and now it is reduced to 10. Is it good or should we disconnect the filter? Please help me.

Best regards
Thanking you

71. It is safe to drink, but might not be very palatable

Dear Mr. Moslemi,

TDS upto 500 is generally considered to be alright for drinking. There is no need for RO here. When the TDS is very less (like yours) generally the water tends to taste very flat. But the water is safe to drink.

Related comments from experts on this subject:

Hope this was useful.

Seetha Gopalakrishnan
India Water Portal Team

72. Install a TDS controller

There is nothing to worry as you are getting 99% rejection.

If it happens ask the purifier service agent person to install a TDS controller and to blend only if you have UV purifier attached to it .

Thank you
Zarna water technology

73. When TDS is 553, what kind of water filter should we use ?

We use ground water (through bore) and the TDS is 553. What kind of water filter should we use ? Sometimes when I open the tank, I have seen a white layer floating in the water.

74. TDS level of tap water 88 but with new RO system it is 8


We have recently got installed a RO+UV system to have good quality water as recently there were cases of jaundice in my family, our tap water has TDS of 88 and the new water purifier has TDS of 8. Kindly suggest whether to continue with RO+UV purifier or not. Some salesman was telling me that at 88 TDS, only a UV water purifier will work better than the RO+UV.
Kindly let me know what kind of purifier to go for considering that I live in Delhi and few cases of jaundice have cropped up.


75. Need help: RO system not reducing of TDS 1800

I have relocated to new locality in Faridabad, Haryana where TDS content in water supplied is 1800. My RO system which was working fine since years, it is now not supporting me to reduce the TDS quantity.

Please suggest.

76. TDS in drinking water - Are we losing essential minerals

Our bore well's TDS was found to be ~800. Recently we purchased aquaguard RO system. After filtration it is showing ~80 TDS. Is this safe for drinking or else, are we losing any essential minerals? Please clarify.

77. Water conditioner as softener and cloriform bacteria treatment

We have TDS varying between 700 to 900 and the water has coliform bacteria of 200. We want to install a water softener for our building complex using 50000 liters/per day.

The solutions being considered
1) A vendor suggested that we go for a new technology called "Water Conditioner" which will not scale our pipe - in fact will remove the scales from the clogged pipes in next 2-3 months, We can expect the discharge of the scales from our taps during this period. None of our equipments like washing machines , geysers and of course pipes will have scales. The water will get heated fast like that after the use of salt based softener. The TDS from the water does not get reduced when treated thru "water conditioner". For drinking we can continue to use RO systems.
2) Regarding the presence of Cloriform bacteria - it was suggested that we should use chlorine and pass it thru activated carbon to neutralize the taste and effects of chlorine.

Would welcome suggestions and experience of people in this forum.

78. Better to locate the source of coliform contamination

Dear Mamta

The magnetic water conditioner can be tried safely. But as far as the coliform bacteria are concerned (not chloriform), it is better to locate the source of the contamination of the sewage rather than chlorinating and passing it thro' a filter which are anyway laborious to do on a regular basis.

If you give me details of your residence, how the used water in your premises is disposed off (particularly the sewage) and whether you have sewerage connection, I may be able to give you hints for where to look for the contamination.

Indukanth Ragade(

79. MCD supply water, TDS 100 - which purifier system do I go for?

Which purifier system RO or UV is good for soft water with 100 TDS? Please suggest.

80. Feasible/ economical way of reducing TDS of irrigation

Dear sir,

My irrigation water's (open well water) TDS is 1350 ppm, I want to reduce it to 500 ppm to give goods results from my gerbera plants. Should I go for RO or please suggest the feasible/economical way of reducing TDS of irrigation.


81. Please suggest methods of analysis of TDS in ETP

We have recently checked the nature of inorganic TDS in our treated effluent (ours is the Effluent Treatment Plant) which treats waste water from 2  paper machines making coated paper). TDS includes 86.5 % of inorganic part & 13.5 % part of organic part. We wish to know more details about these 86.5% part inorganic content. Please suggest what are the methods of analysis to find which salts /compounds are present in the effluent as an inorganic part?

82. Borewell TDS 950 - need help to right RO filter

Dear Sir,
Our bore-well water has a TDS of 950. There is no taste in the water and it consists lot of iron impurities which also makes our white clothes yellow. We used to boil the water for drinking, but after checking it was noted that boiled and further cooled water is having TDS of 850. So I am planning to buy RO based water purifier. Please suggest which water purifier is good for this TDS level and what should be the minimum TDS level. As per the reviews upto 500 mg/L is fine to drink. Though the borewell water which I am using has a TDS of 950, there is no taste in it and water lines also gets chocked regularly.

J K Saraff

83. Boewell TDS 950 - need help to right RO

Dear Mr.Saraf ,

Your TDS of 950 is within the limits for drinking water and does not need any further treatment from the point of view of dissolved salt content. You however have micro-quantities of iron salts also which are in the dissolved state when under the earth but on being drawn out, get access to oxygen in the air and get converted into insoluble form and come out as yellow sediment which spoils the taste and also stains clothes. You will have to install an iron removal plant to get rid of the iron salts. Please dont waste money on an RO plant. If you let me know your email id, I will give you some ideas which may enable you to solve the problem without the iron plant. Indukanth Ragade (

84. Is there a way to prevent water wastage? இதை தடுக்கமுடியாதா?

பூமியில் இயற்க்கையான நல்ல தண்ணிர் 10 TDS to 200 TDS வரை எதிர்மறை சவ்வூடு முறையில் தண்ணிர் பிரிதெடுக்கும் போது நிலதடினீர் கிட்ட தட்ட 3ல் இரண்டு பங்கு தண்ணிர் மாசுபடுகிறதே அல்லது நிலத்தடினீர் தேவையில்லாமல் வீனடிக்கபடுகிறதே இதை தடுக்கமுடியாதா?

Naturally good quality groundwater with a TDS between 10 and 220, when subjected to RO results in huge wastage of water (close to two-thirds of the water is wasted, only one-third is purified and usable). Is there any way to prevent such an unnecessary wastage of good quality groundwater?

85. Need help with low cost treatment plant suggestion to reduceTDS


The domestic water supply source for Puducherry is tubewell. Day by day the TDS level is getting increased. RO system will be costly and will also more skill needed for maintenace. Suggest alternate method of treatment for TDS reduction for domestic water supply which should also be maintenance free. (Reduction from TDS- 1500 mg/l to 450 mg/l required).


86. Need a little more details from you to suggest ways to help you

Hi Sundaramoorthy

Give me the following details to see how I can help you:

  • Is the area close to the sea?
  • while digging the tubewell, at what depth did you start getting water?
  • How did you decide that the TDS is 1500?
  • Are there any dug wells in your area?
  • Has the tubewell digger given you any report on the construction of your tubewell?
  • When you pump for the first time in the morning, collect a tumbler after 1 minute of pumping and after 5 minutes of pumping and see whether there is any difference in the quality of the two samples.

Indukanth Ragade (

87. Need detailed analysis of water to suggest ways to tackle issue

Hi Sundaramoorthy,

First of all, we have to see the detailed anslysis of your water i.e. the nature of the salts which make up the 1500 TDS. But on an overall basis, it is water that can be used for all purposes, including drinking, although a reduction in the salt content may be marginally beneficial for drinking purposes.

Why do you want to reduce the TDS? Do you have any report on the construction of the borewell? If you do, let me know as it will give some ideas on how to tackle your problem in an economical way.

Does the quality of the water improve in the rainy season?


88. Purified to remove salts which contribute to its condutivity

With reference to my comment under the above title on August 12th 2012, please read the first sentence as follows:"Water is purified not to reduce its conductivity but the content of the salts in it which contribute to its conductivity."

89. Dear ZWTI am amazed at the

Dear ZWT,

this is in response to your note of 21stDec 2012 in response to my rejoinder of 29th Nov to your earlier note 19th Oct.

The Bureau of Indian Standards has specified that water having upto 500 ppm is ideal for consumption and if not available, even up to 2000 ppm is acceptable. The WHO standard clears TDS upto 1500 ppm for consumption. In the light of this, your statements that water having `1000 ppm is unfit for consumption and only that with 50 ppm is fit', does not stand scrutiny and is grossly misleading to people at large.

Again, you had in your earlier note claimed that one can get reliable TDS meters for only Rs 500. Now you are talking about some American meter that costs Rs 900. You also say ‘It is approved” – approved for what and by whom ? Again, your experience of 12 years in operating, analyzing and repairing machines does not confer any stamp of quality on the meters that you are recommending.

Please also remember that I had cautioned users, that they should buy a reference liquid with known TDS for periodically checking the reliability of the meter so that the reliability of the meter is ensured. That “the body works on ion exchange , nutrition, vitamins ……”, is not relevant to the subject of TDS parameters for potability.

Indukanth Ragade

90. TDS 750 ppm, which kind of purifier should I install?


The TDS of water supplied to our kitchen is 750 ppm, which kind of purifier should I install?

91. What is the minimum value of TDS that is safe for drinking?

TDS of my home RO water is 15. Is it safe to drink it or to what value should I change it. 

What is the minimun value of safe TDS in drinking water ?

92. Details for setting up drinking water treatment plant at Bellary


I would like to start a new drinking water teatment plant with TDS, RO, UV, and Ozone treatments, having a capacity of 500-1000 LPH at Bellary, Karnataka. Please let me know the best configuration for the plant along with the

  • Company Brand Name
  • Cost of the Equipments
  • Area required and any other information that may be useful

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