Total hardness in drinking water samples

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Total hardness is a key test parameter for the potability of water. Kindly advise, testing calcium and magnesium  shall also be required to ensure safe supplies?

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14 Answers

  1. TDS present in water is not a measure of any single contaminant and so is generally not regulated as a health issue by many government agencies. A high TDS level, however, can affect the taste and odour of water. The Environmental Protection Agency in the US has set the  maximum recommended level  of 500 milligrams per litre (mg/L).

    Reports are derived from the World Health Organization, where WHO states that any level of TDS below 300 mg/L is considered as being safe. A level between 300 to 600 mg/L is considered as being a good level, while 600-900 is considered being fair, while 900-1200 is perceived at being poor. On the other hand, a level of more than 1200 mg/L is considered completely unacceptable. In India, the water level above 500mg/L is considered being completely unacceptable. However, the lack of water resources has led to people drinking such water that has exceeded the number of normal TDS levels.

    Moderate to  high TDS in water  not only changes the taste of water but also poses a lot of health hazards.

    Why Do you Need to Measure Total Dissolved Solids?

    Testing the water is a great way to check the quality of water that you receive and use for different purposes. Here are some reasons you need to measure TDS in water.

    Taste- High levels of TDS in water affects the taste of your drinking water. Your water may taste bitter, salty or sulfuric depending on the type of dissolved solids present in water.

    Health Purposes- Water with high TDS is completely safe to drink. However, some substances such as lead, or copper can lead to health hazards.

    Maintenance of Filters- Water filtration systems are affected by a high level of TDS. Testing the water purifier systems regularly will ensure that the filters work properly

    Cooking- Though high TDS doesn’t affect health, it can alter the taste of your food.

    Cleaning- High TDS in water leaves ugly spots on your utensils. This type of water also fades the color of your clothes, lead to a buildup in your sinks, tubs, and faucets.

  2. Dear Uday Prasad,

    I made a survey about the analysis of the most liked bottled water in Italy to appreciate the differences in the salts contents in those. Actually I found remarkable differences in the way to conclude that there is not a salt content assessed for the best quality water.

    In general the Ca++ content is about between 20 and 70 ppm, whilst the Mg++ content is much less than that, for a total salt content between 50 and 150 ppm.

    My statistics are available in India through my Indian licensee Messrs VDT (Trichy - Tamil Nadu)

     

  3. Neither calcium nor magnesium are unsafe at normal concentrations ,<70mg/L. Although at high concentrations, >100mg/L, they can have an impact on the taste of the water.  Sensitive groups, e.g. people who suffer from kidney or gall-bladder stones are likely to notice an increase in stones if they regularly intake water with calcium concentrations of 150mg/L or more.  Magnesium from concentrations of 70mg/L and above can cause infants to get diarrhoea. Diarrhoea becomes a general concern for all consumers once the concentration exceeds 300mg/L, but at this concentration the water is extremely bitter and it is highly unlikely that it will be consumed by an average user. Thus Calcium and Magnesium should be tested, at least initially, to get a baseline. If they are of low concentrations, then it is unlikely they will be problematic.

    1 Comment

    1. Thanks Juan for your detailed response!

      Calcium and Magnesium should be tested, however, routine testing  add to cost.  

      1 Comment reply

      1. Thanks Uday, I don't think routine monitoring for Ca or Mg would be required if the baseline test showed both at low concentrations. Unless the water source is regularly impacted from external sources. Most Labs measure Ca and Mg to calculated the Total Hardness anyway e.g. T.H. = [2.497 x calcium (mg/l)] + [4.118 x magnesium (mg/l)] from a local South African example, so if total hardness is below 300mg/L then Ca and Mg  are likely at safe concentrations.

  4. Total dissolved solids may not increase significantly even if toxic chemicals are present in water in excess of permissible limits. In such a case how to decide on the advisability of RO installation. Is it right to consider only TDS value for deciding on the need for RO installation?

  6. Hardness of Water is not strictly a water safety concern. It is one of the aesthetic characteristics of Water and as colleagues have discussed below Calcium and Magnesium are not considered toxic at the concentrations normally experienced in drinking water. High hardness impacts the ability of soap to lather and therefore May have an impact on cleaning. Also high concentrations of these elements together with carbonate will lead to scaling in Water cooling systems and domestic water heating devices including to kitchen kettle.

  7. @Uday Prasad: Total Hardness permissible as per CPHEEO Manual is 200 mg/l as CaCO3. Checking for Ca+ and Mg+ maybe used for validating the Total Hardness reported. Alkalinity would be another interesting parameter which would give you an idea of Carbonate Hardness aka Temporary Hardness. 

    Total Hardness = Temporary Hardness + Permanent Hardness

    Temporary / Carbonate Hardness can generally removed by boiling water.

  8. Basically the test for the various salts of the elements Ca and Mg is sufficient. However,  the elemental levels of Ca and Mg maybe checked if they are known to be problematic in the region.

  10. As others have noted, hardness is directly linked to calcium and magnesium content of the water, but these do not in general impact on the safety of supplies, but rather on the potential for precipitation and scaling, particularly in hot water systems.  It is usually desirable to differentiate between temporary and permanent hardness, which are a function of the anions (CO3-, SO4) rather than the cations (Ca and Mg).  Temporary hardness causes scaling which can be more easily removed/dissolved than permanent hardness.

    1 Comment

    1. Easily dessolved, how? I would love to learn.
       

  11. In general, yes it should be required to test total hardness, and also magnesium and calcium separated. But ultimately the regulations in each country/region defines that.

    In Brazil, my country, we have to test for total hardness, Calcium and Magnesium for drinking water of any source, despite being connected to the public system or pumping groundwater or rivers and private reservoirs.

  12. Hardness is measured as Calcium carbonate. Most countries do not regulate it because it is not a health risk, and probably beneficial. However, excessive hardness can affect potability and economics because it can build up in pipe and shorten the life of heaters. Some do not like the taste effect on coffee and tea. The USGS classifies hardness as follows:  soft, up to 60 mg/L, moderately hard 60-120, hard 120 -180, very hard above 180 mg/L. It can cause soap lathering and rinsing problems. That's why they invented detergents which have different chemistry than soaps. My water is in the moderately hard category and it is fine. I have never considered buying a water softener. 

  13. calcium and magnesium  could be from the natural sources such as the various geological coditions. Bascically, they are not toxic substances. However, they may deteriorate the tast of the drinking water.

    1 Comment

  14. I'm not exactly sure of the question? If it is about testing for hardness, the best source is Standard Methods for the Examination of Water and Wastewater.  Unfortunately it is an expensive book.  My guess is that one could go to Google and get an answer for free?

    2 Comments

    1. National Green Tribunal of India does not recommend RO if water contains TDS < or= 500 ppm. TDS based recommendation for determining the need for RO is what is being contested. Example: If water contains Arsenic 18micro grams per litr, Chromium > 2 micro gramper litr and Strontium >7mg/litr, water becomes unfit for human consumption even if TDS does not exceed 500ppm necessitating using domestic RO unit.

      UDayashankar

       

    2. The context here is the mini piped water supply schemes  (designed for population size 1000) and large number of deep bore wells spread in the rural areas and small towns. Preliminary understanding of water quality is possible with field testing kits (FTKs) . The objective here is to test a minimum number of safety parameters to understand if water is potable.

      Water samples are being tested for total hardness. My question is if the measured value of total hardness is within the acceptable range then should we tests of Calcium and Magnesium?