Regularly brewed coffee is ninety-nine percent water so it stands to reason that differences in water used to brew coffee with can result in big differences in the cup. When someone asks me how they can improve their coffee at home, one of the first things I ask them about is the water they use. If your water is not pleasant to drink, don’t brew coffee with it. If you have unpleasant water, either filter it, use spring water, or save yourself some money and use instant coffee. To achieve the optimum cup of coffee, these are the water characteristics I believe you need:
1. The water should not be contaminated with any organic compounds (organisms, pesticides, etc.), copper, or lead. This safety guideline is for any water you drink.
2. Don’t use soft water; the water should contain less than 10ppm (see footnote) of sodium. If all the water in your home is softened, you might want to try the water from your outdoor hose hookup.
3. Don’t use water that is too hard. Water that is too hard tends to mute acidity (brightness). This can somewhat be compensated for by using more acidic coffee beans eg. Kenya AA. Water with 20ppm (parts per million to 120ppm of calcium is good. Calcium is essential for good extraction.
4. The water should be clear. This normally is not a problem, but if it is, running the water through about any type of filter should remove such impurities.
5. The water should have no chlorine. Some larger cities water has a noticeable chlorine taste. Water in this area doesn’t seem to have that problem. So, unless you have a well that you chlorinate, you shouldn’t have to worry about it. If you do have a chlorine taste, boiling the water for a while, letting it sit out for a couple days, or running it through a reverse osmosis system or activated carbon filters should solve, or at least mitigate, the problem.
6. Iron and manganese should be less than 0.02ppm. These contaminants don’t pose a health risk, but too high a concentration of either can taste unpleasant. For most people, 0.3ppm of iron and 0.05ppm of manganese in water is objectionable.
7. Use water with a neutral pH. Between pH 6.8 and pH 7.3 is acceptable.
8. The water should be well oxygenated. Water with little dissolved oxygen results in a flat tasting cup. If using bottled water, it’s a good idea to incorporate oxygen by vigorously shaking your water before brewing. If you manually heat your water (ie. don’t use autodrip machine) then take care not to over boil the water because as the water boils, it releases its dissolved oxygen.
9. The water should have total dissolved solids (TDS) of 150ppm ideally, 60 to 250 is good, any higher and there may be some loss in flavor. A TDS meter is needed to determine the TDS of water.
The most common, easiest solved, and quite critical issues I find are that people are using their regular soft water, or using distilled water. Switching from soft water to hard water for brewing coffee makes a very noticeable improvement; and while using distilled water is very benevolent, its logic is misguided as can be discerned from the above guidelines. I hope this helps you brew better coffee at home; and remember that your coffee can only be as good as its weakest component allows. So if you have great beans, but horrible water, you are wasting the beans, and if you have great water and bad beans you are wasting your time. ppm, short for parts per million, it is a measure of concentration equivalent to milligrams per liter.