Build Better Espresso Water
Your water's mineral content shapes every shot. Enter your source, location, and filter to get a custom mineral recipe and machine health assessment.
Saved Water Profiles
Your saved mineral recipes and water assessments. Build a library across different water sources or seasons.
About WaterLab
What this tool does, how it thinks, and how to get the most out of it.
How WaterLab Works
Water is the most underrated variable in espresso. It's about 98% of what's in the cup, and its mineral content directly shapes extraction, flavor, and how fast scale builds up in your machine.
WaterLab takes your location, water source, and filter type and does two things: it estimates your current mineral profile using utility data and published filter correction factors, then compares it against a target profile you choose. If your water is off, it outputs a mineral recipe to fix it.
The Water Source
Tap water, filtered water, distilled water, and RO water all behave differently. Distilled and RO water have almost no minerals, which means espresso tastes flat and the water is corrosive to metal components. Tap water ranges from too soft (flat, sharp) to too hard (muddy, scale-heavy). The goal is the middle: enough magnesium for flavor extraction, enough calcium for body, controlled alkalinity for balance.
Filters and What They Actually Do
Activated carbon filters remove chlorine and taste compounds but leave minerals largely intact. Ion exchange filters (like Brita Standard) reduce hardness by 30-50%. ZeroWater removes almost everything, producing water that's too soft on its own. RO removes 90-99% of dissolved solids. Water softeners swap hardness minerals for sodium, which doesn't help espresso extraction.
Because filter output varies by model, age, and incoming water, WaterLab uses published reduction ranges and flags its estimates clearly. A TDS meter gives you a precise reading and improves every calculation.
The Mineral Recipe
When your water needs mineral additions, WaterLab outputs a recipe in grams per liter using two compounds: magnesium sulfate (Epsom salt) for extraction quality and potassium bicarbonate for alkalinity balance. These are food-grade, inexpensive, and widely available. The amounts scale to your batch size.
Scale Risk and Machine Health
Carbonate hardness is the key scale risk number. When heated, calcium and magnesium carbonates precipitate and stick to boiler walls, heating elements, and flow paths. Scale is an insulator; it makes your machine work harder, throws off pressure, and causes component failure if left untreated. WaterLab assesses your scale risk and recommends a descaling schedule based on your water's hardness.
Location Data
WaterLab uses a curated database of US cities and country-level fallback profiles for international users. US data is sourced from municipal Consumer Confidence Reports (CCRs). All estimates are flagged as estimates; a TDS meter gives you the exact number. If your city isn't in the database, the tool falls back to a regional average and tells you so.
About The Home Barista's Quill
WaterLab is built by Jim at The Home Barista's Quill, a free weekly newsletter for home baristas who want to go deeper. Espresso technique, grinder guides, water chemistry, workflow. If you're pulling shots and want to understand what's actually happening in the puck, it's worth a look.