In Ireland, oyster stouts are brewed with local water and local oysters giving each area a uniquely flavored beer stout. Coffee is often brewed in the home using water from the tap and all the local flavor that comes with it. If you love your home brew, you probably don’t need to read the rest of this, but for those who are looking for a better tasting cup of coffee, read on.
Coffee is mostly water which means you need fresh, filtered water to have a clean canvas for the true taste of the coffee to come through. There are many options for treating, purifying, or filtering drinking water including spring water, carbon or charcoal filters, reverse osmosis, and distilled. Some treated water will work well for brewing coffee and some will not. Water hardness and pH are also important factors, but for today, we’ll focus on the total dissolved solids (TDS). TDS are easily measured, easily adjusted, and have a big impact on the taste of your coffee.
TDS are the soluble organic matter and inorganic salts that are found in water. You need these solids in your water to extract the soluble components of the coffee grounds into your cup. If you remove all of these solids you will be left with a very unsatisfying cup of coffee.
According to the Specialty Coffee Association of America, water, with Total Dissolved Solids (TDS) around 150 (range of 75-250), is ideal for brewing coffee. How do the TDS levels for various treated waters compare? Here’s what we have found through our testing:
Total Dissolved Solids for Distilled and Reverse Osmosis were less than 10. Various bottled and spring water showed TDS between 25 and 95. Tap water provided by our customers for testing their Total Dissolved Solids ranged from 90 to over 800!
I am asked all the time about the water we use at the Roastery for brewing our coffee. For consistent results, we find the reverse osmosis process is the best option to start with since it removes everything except the pure water molecules. Then we take a page from the Irish and add a little of our tap water to the RO water to achieve the 150 TDS level for brewing, as well as achieving a uniquely “local” flavor for our locally roasted coffee.