San Antonio Water System publishes typical hardness 15 to 20 grains per gallon, which puts San Antonio tap water in the very hard band on the USGS scale (soft is 0 to 60 mg/L as calcium carbonate, moderately hard 61 to 120, hard 121 to 180, and more than 180 is very hard). San Antonio has some of the hardest municipal water of any large US city, and SAWS says so plainly. At 15 to 20 grains per gallon you are at the top of every machine hardness scale, and filtration is not optional if you want the machine to last.
What San Antonio Water System publishes
| Where | Published hardness | Class |
|---|---|---|
| Typical SAWS supply | 15 to 20 grains per gallon | Very hard |
Figures above are from Water Quality FAQs, SAWS, fetched and read for this page. Class assigned against the USGS hardness scale. One grain per gallon equals 17.1 mg/L as CaCO3.
What the number actually does inside your machine
Hardness is dissolved calcium and magnesium, and the chemistry is the same in every city: heat the water and those minerals drop out of solution and plate onto the hottest metal in the machine, which is the boiler wall and the heating element. Scale is a good insulator, so a coated element has to run longer and hotter to hit the same brew temperature, which is why a scaling machine loses shot temperature before it loses anything else. The same deposits narrow flow paths and valve seats, which is where slow shots and weak steam come from. None of that is brand specific, and none of it is reversible by cleaning tablets, which handle coffee oils rather than minerals.
Setting your machine for San Antonio water
Most machines with a hardness setting count for you: you tell the machine how hard the water is, and it decides when to raise the descale prompt. Miele states the mechanism directly, that the machine monitors water and steam used and the number of drinks before descaling depends on the hardness level set, and publishes a four-level scale in grains per gallon. Breville uses five levels, Hrd1 to Hrd5, read off the test strip in the box. Match the setting to your measured number rather than the city average, and follow your own manual for the descale procedure itself, since the cycles differ.
| Your hardness | Miele level to set | Breville equivalent | Effect on descale prompts |
|---|---|---|---|
| 0 to 3 gpg | Level 1, soft | Hrd1 | Longest interval between prompts |
| 4 to 7 gpg | Level 2, moderate | Hrd2 to Hrd3 | Prompts arrive on a middling cycle |
| 7 to 15 gpg | Level 3, hard | Hrd3 to Hrd4 | Noticeably shorter interval |
| 15 to 22 gpg | Level 4, very hard | Hrd5 | Shortest interval the machine offers |
| Above 22 gpg | Beyond the scale | Beyond the scale | Miele recommends switching to bottled drinking water instead |
Hardness levels and the descale-counting mechanism from the Miele CM 5200 operating instructions (PDF); Hrd1 to Hrd5 from the Breville Oracle instruction book (PDF). Both fetched for this page. Your model may use a different scale: check your manual.
Put a date on it: feed your San Antonio hardness number into the free descale schedule generator and it returns a dated cycle for your machine, or start from the symptom with the fix your coffee maker hub.
Related reading
- How to test your home water hardness
- Best water for an espresso machine
- Coffee machine error code lookup
- Fix your coffee maker hub
Related reading
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Gear from this guide
FAQ
Is San Antonio water hard or soft? San Antonio Water System publishes typical hardness 15 to 20 grains per gallon, which is very hard on the USGS scale.
Do I need a water filter for coffee in San Antonio? A filter changes what reaches the boiler, and how much it helps depends on your number and your machine. Whatever you decide, set the machine's hardness level to your measured value so its descale counter is honest, and follow your manual's descale procedure.
How do I convert San Antonio's hardness to grains per gallon? Divide the mg/L or ppm figure by 17.1. One grain per gallon is 17.1 mg/L as calcium carbonate.
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