Water Quality for Espresso
Espresso is roughly 98% water, so what comes out of your tap shapes both the flavour in the cup and the health of your machine. Water that is too hard leaves scale in the boiler; water that is too soft tastes flat and can be corrosive.
Targets
SCA-style guidance gives a workable window for espresso:
| Measure | SCA target | Why it matters |
|---|---|---|
| Total dissolved solids (TDS) | ~75-150 ppm | Extracts flavour well; too low tastes flat, too high tastes dull |
| Calcium hardness | ~35-85 ppm | Drives extraction and scale; high hardness builds scale, near-zero can corrode |
Aim for the middle of these ranges for a good balance of taste and machine safety.
Testing your water
- Use the Water Hardness Test Kit dip strips for a quick hardness reading.
- A TDS meter gives a numeric total-dissolved-solids figure if you want more precision.
Test the water you actually brew with, not a generic figure, since tap water varies by area and season.
The scale problem
Hard, mineral-rich water deposits scale inside the boiler and lines. Over time this causes:
- Slow or restricted flow
- Temperature instability
- Eventual damage to heating elements and valves
The fix is prevention: filter the water, and/or descale on a regular schedule set by how hard your water is.
Choosing water
- Filtered tap water is the simplest good option for most people.
- Remineralised low-mineral water gives the most consistent results batch to batch.
- Avoid distilled or zero-TDS water on its own. It tastes flat and can be aggressive toward some boilers, since water with almost no minerals tends to pull them from wherever it can.
Dialling in flavour but the water checks out? See dialling in. To keep the machine healthy long term, pair good water with routine descaling.