Water testing tools
Step-by-step guide for the digital pH/TDS/EC meter and the API GH & KH test kit. Practical companion to Lesson 1.4: Water.
Bonus content locked
This guide unlocks after completing all 4 lessons in Phase 1: Coffee Fundamentals.
Why test your water?
Your coffee is 98% water. Its mineral composition determines how flavors are extracted. The digital meter tells you how many minerals are present; the API kit tells you which ones they are. Together they give you the complete picture.
Total Dissolved Solids
How many minerals your water has in ppm. This is the most important measurement for coffee.
Acidity / Alkalinity
SCA recommends water between 6.5 and 7.5 for coffee.
Electrical Conductivity
Measures the same as TDS but in µS/cm. For coffee, focus on the TDS reading directly.
Calibration (first time only)
Repeat every 2-3 weeks or if readings seem off.
Prepare the buffer solution
Dissolve the pH 6.86 powder packet in a glass with distilled water (~250ml). Stir until completely dissolved.
Submerge the electrode
Turn on the meter, submerge the tip in the buffer solution. Wait a few seconds for the reading to stabilize.
Press CAL
Hold down the "CAL" button for 5 seconds. The number will flash and then stabilize — that means it calibrated.
Repite con pH 4.01
Rinse the tip with distilled water, then repeat the process with the pH 4.01 packet. With two calibration points your meter is accurate across the entire range.
How to measure your water
Sirve el agua en un vaso limpio
Use the water you want to measure: tap, jug, bottled. Don't use the same glass — rinse it between mediciones o usa vasos separados.
Enciende y sumerge
Turn on the meter, submerge the tip in the water. Gently move it in circles 2-3 times to remove air aire.
Espera ~30 segundos
Let the number stabilize. When it stops moving, that's your reading. You can press "HOLD" to lock the number on the screen.
Anota en tu cuaderno
Registra: tipo de agua, TDS (ppm), pH, y fecha. Con el tiempo vas a tener un historial que te ayuda a elegir tu agua ideal.
Enjuaga entre mediciones
Moja la punta con agua destilada antes de medir otra agua diferente. Esto evita contaminar la lectura.
TDS doesn't require calibration — it comes factory calibrated. Only pH requires calibration with thelvos buffer.
General Hardness (General Hardness)
Measures the calcium + magnesium in your water. They're the "extractors": the minerals that unlock the coffee's flavor compounds.
More magnesium → brighter, more acidic coffee
More
calcium → rounder, fuller-bodied coffee
SCA recommends: 50-175 ppm
Carbonate Hardness (Alkalinity)
Measures the bicarbonates in your water. They work like a "volume control" for the coffee's acidity.
Low KH → aggressive acidity
High KH → flat, lifeless
coffee
SCA recommends: 40-70 ppm
Conversion
Cada gota = 1 dGH (o dKH) = 17.9 ppm
Ejemplo: 4 gotas × 17.9 = 71.6 ppm
Test KH (Alkalinity)
Cambio de color: blue → yellow
Llena el tubo
Use the glass tube from the kit. Fill it with 5 ml of your water (up to the marked line).
Agrega 1 gota del reactivo KH
Hold the KH reagent bottle vertically and add one drop only.
Tapa e invierte
Cap the tube and flip it several times to mix well. Observe the color.
Repite gota a gota
Keep adding drops one at a time, shaking after each one, until the water changes from blue to yellowo.
Calculate your result
Number of drops × 17.9 = your KH in ppm
Test GH (General Hardness)
Cambio de color: orange → green
Clean tube with fresh water
Rinse the tube and fill it with 5 ml of fresh water (don't reuse water from the KH test).
Agrega 1 gota del reactivo GH
Usa el frasco de reactivo GH (diferente al de KH). Agrega una gota.
Tapa, invierte, observa
Repite gota a gota hasta verde
Calculate your result
Number of drops × 17.9 = your GH in ppm
If the very first drop already changes the color, your water has very low hardness. This is common in reverse osmosis jugs and means your water lacks enough minerals to properly extract the coffee's flavors.
What are they?
Paper impregnated with chemical indicators that change color based on the liquid's pH. It's a quick, analog way to measure pH — less accurate than the digital meter (±0.5 vs ±0.01), but useful as a quick check.
How to use them
Arranca una tirita
Separa una tira del bloque de papel. Sostenla por un extremo sin tocar la zona que vas a sumergir.
Sumerge brevemente
Dip the strip in the liquid for just one second — don't leave it soaking. Pull it out immediately.
Espera 15-30 segundos
Deja que el color se estabilice. No la toques mientras cambia.
Compara con la escala
Hold the strip next to the color scale printed on the box. Use natural light and a white background — artificial or yellow light can trick you.
Escala de colores y significado
As a quick check if you doubt the meter's calibration, or to measure liquids where you don't want to dirty the electrode (like prepared coffee, out of curiosity). For serious water measurements, use the digital meter.
Exercise: Complete water profile
This exercise goes beyond what lesson 4 asks — it's what competitive baristasncia.
Mide 3 aguas diferentes
Your tap water, your jug, and a bottle of bottled water (~100-130 ppm). Measure TDS, pH, GH, and KHg> de cada una.
Llena la tabla
Record everything in your tasting notebook. Here's a reference:
| Measurement | SCA Target | Your tap | Your jug | Bottled |
|---|---|---|---|---|
| TDS (ppm) | 75–150 | |||
| pH | 6.5–7.5 | |||
| GH (ppm) | 50–175 | |||
| KH (ppm) | 40–70 |
Brew the same coffee with the 2 most different waters
Use exactly the same recipe: same coffee, same ratio, same grind, same temperature. Only change the water.
Prueba y conecta
Did the water with more GH extract more flavor? Did the one with more KH suppress acidity? Note your observations.