Using Water Quality Report Parameters in Homebrewing

Determine what the appropriate concentration of contaminants is in order to brew tasty, impurity free beer.

| July 2019


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Many minerals and compounds occur naturally in water, dissolving into solution from various environmental sources. Some manmade compounds can also be found in water, but these are usually unwanted and referred to as contaminants. Contaminants can be natural as well: molds, bacteria, nitrates, etc., are all naturally-occurring water contaminants. The main purpose of water treatment is to remove these contaminants and the purpose of a water quality report is to inform the public about the types and levels of these substances in the water supply.

We will start our review of a water report by identifying the key constituents—the main ions, chemicals and compounds in typical water supplies. Next, we will show you where to find them on an example of a typical (USA) water report. Actually, there really is no such thing as a typical report. In the USA, the Environmental Protection Agency and the Clean Water Act mandate the testing and disclosure of a specific list of harmful contaminants, which does not include the ions that brewers are most concerned with—calcium, etc. Often these ions are included in a water report, but that decision is up to the water supplier.

Typical water quality reports focus on how the water complies with safe drinking water laws for contaminants like pesticides, micro-organisms, and toxic metals. These items are regulated by maximum contaminant levels (MCL) and referred to as the Primary Drinking Water Standards in the United States. MCLs are legally enforceable standards for water quality that protect public health. While the primary standards are important for assuring water quality, as brewers, we are usually more interested in the Secondary or Aesthetic drinking water standards. Secondary Standards are guidelines for parameters that affect taste, pH, and carbonate scale and are often specified by secondary maximum contaminant levels (SMCL) that are not legally enforceable in the United States.

In many areas, the source of the public water supply can change seasonally, and can often make a big difference in brewing character. Brewers should contact the water department at least monthly to get current information. The water department is usually happy to supply information on the Secondary Standards for brewers. However, not all utilities test for all the parameters brewers are interested in. In that case, the brewer may have to test the water at an external laboratory or perform inhouse testing of the parameters. The cost of equipment and reagents for such in-house testing can, however, be prohibitive.

Of the parameters of interest to brewers, the principal ions affecting brewing water performance in mashing and fermentation are calcium (Ca+2), magnesium (Mg+2), and total alkalinity as CaCO3, which is sometimes simply, though inadequately, listed as bicarbonate(HCO3-1). Their interaction in the mash tun, boil kettle and fermentor influence the pH and other factors throughout the brewing process. Sodium (Na+1), chloride (Cl-1) and sulfate (SO4-2) can influence the taste of both water and beer, but generally do not affect pH or fermentation performance like the first three ions mentioned above. Ion concentrations in water are typically presented as parts per million (ppm), or milligrams per liter (mg/l), which are generally equivalent in dilute solutions like drinking water, one liter of which weighs about one kilogram.

Key Brewing Parameters in Water Quality Report for the Source Water

Primary standards have maximum contaminant levels (MCL) that are legally enforceable requirements in the USA. Secondary Standards are official guidelines and typically have (unenforceable) secondary maximum contaminant levels (SMCL). Unregulated Standards are industry guidelines.

Brewing source water recommendations are indicated in italics. These recommendations are for the source water only.

Alkalinity (as CaCO 3)

  • Category: Unregulated
  • Parameter(ppm): 0-100 brewing
  • Why: High alkalinity is problematic for mashing and promotes carbonate scale when combined with calcium and magnesium.


  • Category: Primary
  • Parameter (ppm): <0.01 MCL <0.01 brewing
  • Why: Disinfection byproduct, Industrial contaminant. Possible carcinogen.


  • Category: Unregulated
  • Parameter(ppm): 50-150 brewing
  • Why: Fermentation, Clarity, Mash pH


  • Category: Primary
  • Parameter (ppm): <4 MCLG 0 brewing
  • Why: Residual disinfectant that can cause off-flavors in beer.


  • Category: Secondary
  • Parameter (ppm): <250 SMCL 0-100 brewing
  • Why: Beer flavor—emphasizes malt character.


  • Category: Secondary
  • Parameter (ppm): <1 SMCL <1 brewing
  • Why: Copper is a toxin at high doses but is otherwise a nutrient. Oxidation catalyst in beer.

Haloacetic Acids (HAA5)

  • Category: Primary
  • Parameter (ppm): <0.060 MCL <0.060 brewing
  • Why: Disinfection byproducts and probable carcinogens.


  • Category: Secondary  
  • Parameter (ppm): <0.3 SMCL 0 brewing
  • Why: Off-flavor, scale, corrosion risk.


  • Category: Unregulated
  • Parameter (ppm): 0-40 brewing
  • Why: Fermentation, Clarity, Mash pH, but also supplied by malt.


  • Category: Secondary
  • Parameter (ppm): <0.05 SMCL 0 brewing
  • Why: Off-flavor, scale, precipitation causes gushing.

Nitrate as N Nitrate

  • Category: Primary
  • Parameter (ppm): <10 MCL(as N) <44 MCL (NO 3) <44 brewing
  • Why: Excessive nitrates can indicate agricultural runoff. Nitrates can be reduced to Nitrites.

Nitrite as N Nitrite

  • Category: Primary
  • Parameter (ppm): <1 MCL (as N) <3 MCL (NO 2 ) <3 brewing
  • Why: Nitrites are a food preservative and as such are poisonous to yeast cells.


  • Category: Secondary
  • Parameter (ppm): <25 SMCL<25 brewing
  • Why: Scale former and damaging in boiler systems and membrane systems.


  • Category: Unregulated
  • Parameter (ppm): 0-50 brewing
  • Why: Beer flavor—less is generally better.


  • Category: Secondary
  • Parameter (ppm): <250 SMCL 0-250 brewing
  • Why: Beer flavor—emphasizes hop character and dryness.

Total Dissolved Solids

  • Category: Secondary
  • Parameter (ppm): <500 SMCL <500 brewing
  • Why: Increase indicates high mineralization and greater scaling potential

Trihalomethanes (THM)

  • Category: Primary
  • Parameter (ppm): <0.1 MCL <0.1 brewing
  • Why: Disinfection byproducts and probable carcinogens.


  • Category: Secondary
  • Parameter (ppm): <0.5 ntu SMCL <0.5 ntu brewing
  • Why: Increase indicates contamination and higher scaling potential

What Is an Ion?

An ion is an atom or group of atoms that has a net positive or negative charge, due to the loss or gain of electron(s). An ionic compound is a polar molecule composed of 2 or more ions that are held together by ionic bonds (i.e., electrostatic attraction). The electrical charge of an ion is indicated as a superscript after the chemical symbol for the ion. Positively charged ions are called cations (pronounced “cat-ions”), and negatively charged ions are called anions (pronounced “an-ions”). For example, the mineral sodium chloride (NaCl) dissolves into the cation Na+ 1 and the anion Cl -1 . The hydrated mineral calcium chloride (CaCl 2 •2H 2 O) dissociates into 1 Ca +2 , 2 Cl -1 , and 2 water molecules. Note that the sum of the positive and negative charges for any ionization products from a single compound is always zero. For example, the +2 charge of the calcium and the two -1 charges of the chloride ions sum to zero.

Throughout this text, we will refer to either dissolved minerals and/or ions and mean essentially the same thing—if we refer to a mineral such as calcium sulfate or calcium carbonate being in the water, we are assuming that it is dissolved and dissociated, in accordance with any natural limits such as its solubility constant.

This is also a good point to state that the sum of the dissolved cations and anions in a natural water supply must sum to zero as well. If they do not, it may be that the stated composition is a list of averages, or that it’s the result of different tests for different ions taken throughout the year. The point is that the concentrations of charges of dissolved ions in water must sum to zero at any given moment in time.


More from Water:

Water: A Comprehensive Guide for Brewers by John Palmer and Colin Kaminski. Copyright 2013 Brewers Association. Reprinted with permission from the publisher; all rights reserved by the original copyright holder.



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