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Proper Water Quality for Coffee, Espresso, and Tea

Water and Your Coffee

Coffee is 98.5 to 99 percent water, so, naturally, water quality will critically affect the taste of your brew. Water should be fresh; if it has been sitting too long (or has been heated and then cooled), it will be missing the dissolved air that is an important component of the water's taste. The water should also start cold; hot water has lost some of its dissolved air, and may have picked up minerals or solubles from your pipes. When making coffee, you should only use water that tastes good enough to drink straight. As a result, the best cups of coffee are made with filtered tap water or bottled water. Do not confuse distilled or reverse osmosis (RO) water for filtered; the first two are missing minerals that contribute to the water's taste and aid in extraction. While too much mineral content will hasten damaging limescale buildup inside your coffee maker or espresso machine, an absence of minerals will give the your coffee and espresso a flat taste while also harming the boiler inside the machine.

Water Hardness

Water Hardness Map About 80 percent of the nation's tap water supply is considered to be hard to some degree. Calcium and magnesium in the form of carbonates dissolved in water are the two most common minerals that make water "hard." Hard water requires more soap and synthetic detergents for home laundry and washing, and contributes to scaling in boilers (note: your coffee maker's heating system) and industrial equipment. Quality coffee starts with identifying what type of water you have. Is it hard or soft? By simply testing your water with test strips, you can tell its makeup. Test strips can be found at any hardware or pool supply store. It is recommended that water hardness be no more than 50 parts per million (ppm) / 50 mg/L for optimum performance.

The map to the right shows concentration of hardness as calcium concentrate, in milligrams per liter. Mean hardness as calcium carbonate at NASQAN water-monitoring sites during the 1975 water year. Colors represent streamflow from the hydrologic-unit area. Mape edited by USEPA, 2005. Modified from Briggs and others, 1977.

Limescale Build-Up

There are a number of scientific equations (accounting for factors such as hardness, pH, alkalinity, and total dissolved solids) that can tell us when water will leave a scale build-up inside your boiler and internal plumbing. Simply put, at near boiling temperatures, the minerals that cause hardness will "separate" from the water forming precipitates (solids). This also happens at near freezing temps as well. If you have hard water, and no water softening equipment, take a close look at your ice water sometime. All those white "specks" are the mineral precipitates. Inside your coffee maker or espresso machine's boiler, these minerals coat every surface and harden, literally forming rock. Over time, this build-up reduces heating efficiency, restricts water flow, and damages valves. There are a number of ways to treat the water and slow this damaging process to a crawl. We will start with the methods you do not want to use.

Alkalinity Map
This map provides a synoptic illustration of the national patterns of surface water alkalinity in the conterminous United States. Alkalinity is the most readily available measure of the acid-neutralizing capacity of surface waters and provides a reasonable estimate of the relative potential sensitivity of lakes and streams to acidic deposition. Although the actual sensitivity of a water body depends on many watershed characteristics and processes, the low-alkalinity areas on the map indicate where sensitive surface waters are most likely to be found.

The map is based on alkalinity data from approximately 39,000 lake and stream sites and the associations of the data values with factors such as land use, physiography, geology, and soils. Data were acquired from a variety of sources including federal and state agencies, university researchers. and private corporations. In many of the areas represented by a specific alkalinity range, an even greater range was observed in the water quality data. The shading on the map indicates the range of alkalinity within which the mean annual values of most of the surface waters of the area fall. Earlier alkalinity maps (1,2) depicted more generalized patterns of surface water alkalinity for the United States because of data base limitations and compilation conducted on small-scale maps. This map was compiled using more data and larger scale maps to provide a more precise national picture of surface water alkalinity. Click here to download a high-res version of this map.

Distilled and Reverse Osmosis (RO)

The process of distilling/deionizing (DI) water or treating it through RO nearly removes all minerals, impurities, and other ions in the water. First and foremost, this gives any coffee product made with such water a flat taste because the coffee's aroma particles will not completely transfer to the water. More importantly, this kind of water is actually considered corrosive with a pH of about 5. Distilled and RO water will also strive to return to a neutral state by leeching the copper, brass, or aluminum from the internal parts of your brewing equipment like the Ascaso Dream. Over time, and depending on the extent of use, enough metal could be removed causing an electrical short or a leak. Also, heat exchanger espresso machines like the Nuova Oscar or Pasquini Livia, use electromagnetic sensor to detect water levels and will not function properly with these types of water. If you choose from the Jura-Capresso line of products, this is not a problem because of their stainless steel-lined heating systems, but taste would still be an issue. If you have a home RO system and want to use that water with your equipment, it is advisable to install a mineral or pH-balancing unit to protect your machine and any household copper plumbing.

Softened Water

If you use a properly maintained water softener in your home or business, your water will be considered "boiler safe." There will still be a small amount of minerals, but a low enough concentration that limescale build-up takes months or years instead of days. Water softeners operate on the ion exchange process. In this process, water passes through a media bed, called resin. The ion exchange process takes place as hard water passes through the softening material. The hardness minerals attach themselves to the resin beads while sodium on the resin beads is released simultaneously into the water. When the resin becomes saturated with calcium and magnesium, it must be recharged. The recharging is done by passing a salt (brine) solution through the resin. The sodium replaces the calcium and magnesium which are discharged in the waste water. Hard water treated with an ion exchange water softener has sodium added, and so it is recommended to further treat your water with an activated carbon or a carbon block water filter. These kinds of filters also remove other impurities that affect taste, but, on their own, are not able to remove water hardness. This includes your refrigerator or sink-mounted filters.

Bottled Water

Commercially bottled water comes in many forms: distilled, reverse osmosis, drinking, spring, and mineral. Never use mineral water, as it is, by design, extremely hard. Spring water can be hard or soft, but depends on the source. We already have discussed the distilled and RO water, but in the case of drinking water which uses either of these methods, the water is USUALLY safe to use only if it says it has been enhanced with minerals or pH balanced. The reason for this is that most suppliers post-treat the RO water with a small amount of minerals to neutralize the water's pH. Before settling on a brand of bottled water, it is advisable to check the hardness with a test kit.

Internal Water Filter

Major automatic coffee center brands such as Jura-Capresso and Saeco employ special filters that plug into the water tank. These filters, such as Clearyl and Aqua Prima are optional parts that sometimes come included with new and refurbished units. The filters contain both carbon and organic compounds that will remove both taste altering impurities and most water hardness. Rated for between 50 and 75 liters, they are an excellent alternative to seeking out favorable sources of water. Additionally the digital Saecos and ALL Jura-Capressos will tell you when it is time to change the filter. A rechargeable water softener cartridge is also available for the Rancilio Silvia and other machines that use a hose to draw water from the reservoir. These can be used over and over and only require a saltwater solution to recharge (like a home water softener, only smaller).


Regardless of the type of water you're using, you will need to descale or decalcify on a regular basis, with harder water requiring more frequent descaling. A good rule of thumb is every two to three months, depending on hardness and use. When you decalcify your machine, you are removing the mineral and calcium build-up that has accumulated in the boiler, brew group, frothing wand and other related parts. Descaling products come in powder, liquid, and tab forms. Most super automatic espresso machines, such as Jura-Capresso and Saeco have digital displays that automatically notify you when decalcification is needed. If your machine does not have this option, you will have to remember to decalcify the machine on a regular basis. And when it is time, you should refer to your owner’s manual for complete instructions. Descaling and decalcifying your machine on a regular basis will keep your machine running smoothly for many years to come because removing limescale build-up allows your machine to maintain constant brew and steam pressure as well as temperature.

SCAA’s Water Quality Standard Chart

Target Lower Limit Upper Limit
Odor Clean/Fresh, Odor Free
Color Clear Color
Total Chlorine 0 mg/L 0 mg/L 0.5 mg/L
TDS 150 mg/L 75 mg/L 200 mg/L
Calcium Hardness 4 grains or 68 mg/L 1 grain (17 mg/L) 5 grains (85 mg/L)
Total Alkalinity 40 mg/L At or near 40 mg/L
pH 7.0 6.5 7.5
Sodium 10 mg/L At or near 10 mg/L



Water should be odor free. Any obvious smell (i.e from sulfates, bacteria, chlorine) should be removed Calcium hardness is the amount of hardness created just by calcium ions. Too much calcium may be responsible for scale build up in your coffee equipment.



Should be clear to the naked eye. Cloudiness, color, or particulates should be treated. Alkalinity is the concentration of negative ions in your water. Too much alkalinity can affect extraction and flavor.



Chlorine is added to water to prevent contamination. Chlorine can cause your water to taste or smell different. All chlorines should be removed. Pure water should have a neutral pH of 7. High pH in water will result in a “flat” taste.



Total Dissolved Solvents (TDS) is recommended by the EPA to be below 500 mg/L. TDS usually indicates hard water. Most water contains less than 20mg/L of sodium. High sodium can affect the way flavor is perceived. Avoid high sodium amounts.

Kubota , L. (2013, July 8). Dissecting SCAA’s Water Quality Standard. Retrieved from
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