Adjusting brewing water

What you need

• The water report from your water supplier (usually on its website)
• Distilled or reverse osmosis (RO) water
• Calcium chloride and gypsum
• 80 % lactic acid
• A scale accurate to 0.1 g (0 oz) and a syringe for the lactic acid
• An alkalinity drop test from an aquarium shop and a pH meter

Step by step

1. Step 1Look up your water values

   Find the values for your water: alkalinity, calcium, magnesium, sulphate and chloride. Enter them in the brewing water calculator.

2. Step 2Choose your targets

   A Pils needs rather soft water with little hardness. Pale ale and IPA like more sulphate, hazy IPA and malty beers more chloride. Dark beers can take higher alkalinity because dark malts acidify the mash themselves.

3. Step 3Dilute

   If your water is very hard, mix it with distilled or RO water. This lowers all values evenly, including the alkalinity.

4. Step 4Add the salts

   Weigh out calcium chloride and gypsum carefully and stir them into the cold water until they have dissolved.

5. Step 5Measure alkalinity and acidify

   Now measure the alkalinity. Then add the calculated amount of lactic acid in two portions, stir well and measure again. Wear gloves and safety glasses.

6. Step 6Check the mash pH

   Measure the pH of a sample cooled to 20 °C (68 °F) 10 to 15 minutes after mashing in. The target is 5.2 to 5.6. If it is higher, correct with a little lactic acid.

Tips and common mistakes

• Chloride makes beer softer and maltier, sulphate drier and more bitter. The ratio between the two matters more than the exact numbers.
• After the salts, calcium should be at least 50 mg/l. It helps the enzymes in the mash, the yeast and clarification.
• Your supplier’s values vary through the year. Your own alkalinity test before each brew day makes the calculation more accurate.