Interpreting Water Bottle Labels

Firstly a caveat, I’ve not tested a bottle of water that actually matches the label some are close, some are miles off so although these calculations are pretty accurate the end results may not be as expected. You can easily test Hardness, Alkalinity, pH and TDS at home, most other figures need more advanced test equipment.

 

What are the key figures on bottled water when it comes to brewing coffee?

The units of mg/L and ppm are interchangeable.

Ca mg/L

Mg mg/L

Bicarbonates mg/L (or ppm)

TDS or Dry residue mg/L

pH

 

What am I aiming for?

Total Hardness = 68-100 mg/L as CaCO3

Alkalinity = roughly half total hardness, can be slightly higher for espresso

TDS = 125 – 175mg/L

pH = 7

 

How do I get there?

You’ll notice that some of the figures on the bottle aren’t the same as those we are aiming for, luckily they are easy to calculate.

 

Calculating Total Hardness

Total Hardness as CaCO3  = (Ca x 2.5) + (Mg x 4.2)

Alkalinity = Bicarbonates * 0.82

 

So a worked example for Clearview would be

Label gives us

Ca = 15mg/L

Mg= 5mg/L

Bicarbonates = 45mg/L

TDS = 100

pH = 6.3

Total Hardness = (15 x 2.5) + (5 x 4.2) = 58.5 mg/L as CaCO3

Alkalinity = 45 x 0.82 = 36.9 mg/L as CaCO3

Comments on Clearview – Slightly lower than ideal Hardness, ratio of 1.6:1 Hardness to Alkalinity which is also lower than ideal. pH of 6.3 is slightly more acidic than desirable and the TDS of 100 is also lower than desirable. All of these factors could add up to produce a clean cup with low body and something slightly bland or dull but that’s for another post.

Hopefully this gives you some useful tools to read and understand water bottle labels, there will be more posts on water in the future including how to make your own recipe from scratch.

10 Comments. Leave new

  • Hi!
    I’ve been logging water labels in order to find the best mineral water for coffee here in Portugal. I would like to know where you got those formulas:
    Total Hardness = (15 x 2.5) + (5 x 4.2) = 58.5 mg/L as CaCO3
    Alkalinity = 45 x 0.82 = 36.9 mg/L as CaCO3
    Where do you get the 2.5, 4.2 and the 0.82 values?
    Thanks!

    Reply
  • Spencer Webb
    April 15, 2015 7:34 pm

    Hi goncalo,

    The numbers that you mention come from the difference in molecular weight of Ca+, Mg+ and HCO3- Ions and Calcium Carbonate, this is how water hardness is expressed hence we have to convert.

    With this information in mind then the molecular mass of a Calcium ion is 40g/mol the molecular mass of Calcium Carbonate is 100g/mol. Since 100/40 = 2.5 this is what you must multiply the Ca ion mass by to get to the Calcium Hardness. This follows through for Magnesium but Bicarbonates are slightly different as 2 Bicarbonate ions are formed from 1 Carbonate ion so you have to multiply the molecular mass by 2.

    If you want to follow the equations through for Mg and Bicarb then you can easily google molecular mass of any compound 🙂

    Hope this helps?

    Cheers

    Spence

    Reply
  • Thanks a lot for this article! I rushed immediately to my mineral water comparative (21 waters), to check that the best water in France for espressos is Volvic! In fact this was well known here by the aficionados, but now I know I am compliant with you!
    This water comes from an ancient volcanic massif (Massif Central). Good to know for the travelers, easy to find in all supermarkets.
    (Volvic : hardness:62.4, alkalinity:58.2,TDS=130.0, pH=7.0).

    Reply
    • Off the shelf here in the UK Volvic is also the only thing that comes close. There are some good threads on the coffeeforums.co.uk which detail how to mix waters to get an even better ratio for coffee. Head over there and take a look 🙂

      Reply
  • By the way I have noticed that the TDS is always lower than the sum of the minerals, what is the reason? When they heat the water are there some chemical reactions?

    Reply
    • The measured TDS of carbonates using a standard meter is only around 60% of the actual total. Sulphates and Chlorides etc.. are all 100% though. If you see a difference then this is probably it. Ultimately TDS is a good estimate but that’s all.

      Reply
  • Yes, it is generally from 60 to 70%; sometimes 80, 90, and 1 time 100.9%! I think the labelling is not always very serious… and it can vary with the time. Thank you for your patience!

    Reply
  • Hi,
    Nice blog. Here are the constituents labelled in my water bottle, it would be great that if you could tell me what is the best use of it?
    Nitrate : 1.5 – 2.25
    Chloride : 8-12
    Calcium : 6-7
    Fluoride: 0.09 – 0.2
    Magnesium : 1.5- 3
    pH : 6.5 -7.5
    I would be really grateful if you could let me know the best use.

    Reply

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