And the same question after creating an account and ligging in.
Short answer: **yes—pure RO (reverse-osmosis) water *can* be bad for pipework, boilers, and heating elements in domestic coffee machines if used by itself long-term.**
Here’s why, and what to do instead.
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## Why pure RO water can cause problems
### 1. **Corrosiveness (low mineral content)**
RO water is extremely low in dissolved minerals. That makes it:
* **More aggressive** toward metals
* Able to **leach ions** from copper, brass, aluminum, and even stainless steel over time
In coffee machines this can affect:
* Boilers
* Heating elements
* Solenoid valves
* Copper or brass fittings
Manufacturers often warn against **demineralized, distilled, or pure RO water** for this reason.
---
### 2. **pH instability**
Pure RO water has **very little buffering capacity**.
* Its pH can swing easily
* It often becomes slightly acidic after absorbing CO₂ from air
Acidic, unbuffered water increases:
* Corrosion risk
* Metal ion release
* Premature seal and gasket degradation
---
### 3. **Sensor and control issues**
Many machines rely on **electrical conductivity** for:
* Water level sensing
* Boiler fill detection
RO water’s conductivity can be so low that:
* Sensors misread water levels
* Boilers may overfill, underfill, or trigger errors
---
### 4. **Poor heat transfer & element lifespan**
While scale is bad, *zero minerals* isn’t ideal either:
* Heating elements are designed expecting **some mineral presence**
* Ultra-pure water can shorten element life through micro-corrosion
---
## Why scale prevention ≠ zero minerals
Scale (limescale) forms mainly from:
* Calcium
* Magnesium
But **completely removing them is not the goal**.
The goal is **controlled mineral content**.
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## What coffee machine manufacturers recommend
Most specify something like:
* **TDS:** ~50–150 ppm
* **Hardness:** ~2–4 °dH (30–70 ppm as CaCO₃)
* **Alkalinity:** enough to buffer pH (≈30–50 ppm)
They explicitly warn against:
* Distilled water
* Deionized water
* Pure RO water
---
## Best practices if you use RO at home
### ✅ **Remineralize RO water**
This is the best solution.
Options:
* Commercial remineralization cartridges
* Adding a controlled mineral blend (e.g. calcium + bicarbonate)
* Coffee-specific recipes (Barista Hustle, SCA profiles)
This gives:
* Corrosion protection
* Correct conductivity
* Better coffee extraction
---
### ✅ **Blend RO with tap water**
A simple workaround:
* 70–80% RO
* 20–30% tap water
This:
* Reduces scale
* Maintains mineral safety
* Is widely used in cafés
(Exact ratio depends on your tap water hardness.)
---
### ❌ **Avoid using pure RO long-term**
Occasional use won’t destroy a machine, but:
* Continuous use can shorten component life
* Warranty may be voided if manufacturer specs are ignored
---
## Summary
| Water Type | Safe for Coffee Machines? |
| ——————— | ————————- |
| Pure RO / distilled | ❌ Not recommended |
| RO + remineralization | ✅ Best |
| RO + tap blend | ✅ Good |
| Hard tap water | ⚠️ Scale risk |
If you want, tell me:
* You
r coffee machine model
* Whether it’s boiler or thermoblock
* Your tap water hardness
I can suggest a **safe water recipe** tailored to your setup ☕
