Beer Brewing Water Modification Assistant

Target H2O

Ion Concentrations (ppm)


Target H2O

Source H2O

Diluted Src
Added Ions
Ion Variance

Brewing Salts Added (grams)

Epsom salt


Ion Free Water Dilution %

H2O Volume (gal)

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The Beer Brewing Water Modification Assistant above is designed to simplify the process of calculating the proper quantities of various brewing salts to add to your source water profile in order to duplicate the water of a particular brewing location. If you are duplicating a classic beer, this added step can bring you closer to an accurate final result. For example, I live in Tacoma, Washington and this area has very soft water. If I am attempting to duplicate a Guinness Dry Irish Stout, I might want to modify my water to reflect the very hard brewing water of Dublin Ireland.

Pre-Calculation Steps

  1. Obtain a water analysis worksheet from your local water company. This will have the various ion concentrations of your specific water supply and is necessary in order to know which brewing salts you must add to your water.
  2. Obtain the following brewing salts from your local homebrew supply store: Table Salt (no iodine), Chalk, Epsom Salts, Gypsum, and CaCl2.


  1. Begin by selecting your Target Brewing Water Profile from the pull-down menu. This will fill in the specific ion concentrations of the target brewing area’s water. If there is a location you use on a regular basis and would like me to add it to the list, send the particulars to me via my feedback page. There is also a custom option in this pull-down menu. It simply creates blank fields so you can enter any Target Brewing Water Profile you desire.
  2. Enter the Volume of Water in Gallons you will be modifying. This is found in the bottom section of the calculator.
  3. Enter your Source Water Profile. This is the information found from the chart you obtained from your local water provider. Briefly compare what you have entered to the Target Water Profile.
  4. It is important to note at this point whether your water is harder or softer than the Target Water Profile. If your water is softer (the ion concentrations in your Source Water Profile are lower than the Target Water Profile), you can proceed to the next step. If not, then you must dilute your water with deionized water. You can enter a percentage in the Ion Free Dilution Percentage box until the Ion Free Water Diluted Source Values boxes read lower values than your Target Brewing Water Profile. Once this value is determined, you must dilute your source water to this correct percentage.
  5. Now comes the fun part. You must manipulate the brewing salt values. The brewing salts for this calculator are measured in grams. Anything else is just far too inaccurate. You must begin by entering small amounts in the Masses of Brewing Salts Added in Grams section of the calculator. I usually start with the salts that add Calcium (Ca) to the water. As you change the quantities, you can monitor how each ion concentration changes as the brewing salts are added to your brewing water in the Ions from Brewing Salt Additions section of the calculator. The goal is to get the Variance less Salt Additions section to read zero for as many of the ion concentrations as possible. What this means is the quantities of salts you are adding to your Source Water Profile are adding specific ions to each category of the table. When the proper quantities are added, your Source Water Profile should be fairly similar to the Target Water Profile. Don’t worry about getting it to be exact. Often times this is not possible.

Beer Brewing Water Modification Example

As a final example, for my 5.5 gallon batches of beer, in order for my Tacoma, Washington water to be fairly similar to Dublin, Ireland, I must add: .35 grams of NaCl (Salt), 3.05 grams of CaCO3 (Chalk), .8 grams of MgSO4 (Epsom salt), 4.9 grams of CaCl2, and 1.12 grams of CaSO4 (Gypsum). If you enter these values into the Masses of Brewing Salts Added in Grams section of the calculator, you can see that the Cl- ion concentration will still vary by -87 parts per million. It is impossible to get it to be exact. Good luck and remember to experiment with the values.