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Tips for better brewing with tap water.

Whether it's perfect for brewing right out of the tap or requires a couple of extra steps to eliminate any taints, tap water is the most readily available option for most home coffee brewers. This guide is here to help you determine the suitability of your water for coffee preparation and provide some tips on how you can improve it.

Total Dissolved Solids (TDS)

TDS stands for "Total Dissolved Solids." This represents the amount of "stuff" dissolved in your water. This can be minerals, contaminants, or biological matter. 

Why it matters

TDS is the easiest attribute of water to track for yourself, with consumer-grade TDS meters readily available, reusable, and affordable. 

The ideal TDS for water, based on SCA guidelines, is between 75 and 250 ppm

With TDS, you can broadly measure the mineral concentration of your water. Below 75 ppm, there will not be sufficient minerals to extract and enhance the flavor profile of your cup. Above 250 ppm, your coffee will take on a notable chalky texture and bitter flavors, in addition to accelerated limescale accumulation on your machine. 

Soft vs. hard water

Soft and hard are terms, in this case, that describe the balance of mineral content in water. Hard water is water that has a higher mineral content, while soft water has a lower mineral content. When preparing coffee, magnesium and calcium are the minerals we are most concerned with

Why it matters

Where TDS tells you, in parts per million, how much "not water" is in your water, hardness tells you specifically how much of that is minerals. Just like with TDS, water hardness that is too low will lead to more muted cups, while too high can be bitter, chalky, and lead to faster accumulation of limescale. 

The ideal hardness for water, based on SCA guidelines, is 50 and 175 ppm

Your city published an annual municipal water report that shares the mineral content and hardness of your drinking water.  If you want a more up-to-date and precise measurement, you can also use a home water testing kit or even invest in lab testing. It's important to note that there will be some variance throughout the year, so your results may change.

Water pH and alkalinity

When reviewing your city's municipal water report, you may also see data on the pH and alkalinity of water. 

  • pH (or potential hydrogen) is the measurement of acidity from 1-14, with 1 being the most acidic, 14 being the most basic, and 7 being pH neutral. pH-neutral water will not impart any flavor and will offer a blank canvas for brewing, so it is generally accepted to be the ideal.

  • Alkalinity in coffee is a measurement of water's resistance to becoming more acidic due to the presence of alkali or alkaline earth metals. In itself, alkalinity doesn't make water more basic, but higher alkalinity can balance or even reduce the presence of acid in the final cup.  It can also reduce or diminish the buildup of limescale!

     

Filtration

Finally, if your tap water is not ideal for brewing coffee due to smell, taste, or even hardness, there are still options available to filter out these less desirable elements and help you get the most out of your tap water. 

  • Carbon filter (PUR, Brita, LifeStraw, etc.): Carbon filters work by using highly porous activated carbon to absorb impurities from the water. Carbon filters remove organic impurities, chlorine, pesticides, and bad tastes and odors while leaving the mineral composition of your water intact. 
    Who is it for? Great for tap water that is in the right range for mineral content, but that either tastes "off" or that has too high a TDS due to undesirable dissolved matter.

  • Reverse Osmosis (RO) water or ZeroWater: These products all cover different approaches to bringing the TDS of water down to zero. Zero or near-zero TDS water means zero or near-zero mineral content, which produces especially flat or muted coffee.
    Who is it for? If you have hard water or want to directly control the mineral content of your water, these products can give you a blank canvas to work with. Third Wave Water or similar products, which present a mixture of carefully measured minerals designed for the best brewing experience, can then be added to create the ideal mineral balance and concentration for your coffee brewing at home. 

  • Hybrid filtering: The Peak Water filter is a system that uses two chambers, one utilizing carbon filtering and the other using de-ionizing resin filtering, and allows you to control the ratio of water from each chamber that ends up being processed into your pitcher. De-ionizing resin is one of the methods ZeroWater uses, alongside carbon filtering, to achieve zero/near zero TDS. 
    Who is it for? If you have hard water, this combined approach allows you to control the mineral content without further intervention being necessary.

In conclusion

Tap water is readily accessible and can make for an excellent cup of coffee for many home coffee brewers. With just a few tweaks and a little filtration, you can make sure that the water in your coffee is setting you up for success, so you can focus on grind adjustments and getting the perfect bag.