The Simplest Coffee Experiment You'll Ever Do
You don't need expensive equipment. You don't need formal training. You don't even need to change your brewing technique.
This 5-minute test will prove whether your water is ruining your coffee.
And if it is (spoiler: it probably is), you'll know exactly what you're missing—and how to fix it.
The 5-Minute Water Test
What You Need
- Your usual coffee beans (same bag)
- Your usual brewer (V60, Chemex, Aeropress, etc.)
- Your tap water
- One bottle of Ashbeck or Volvic water (£1 from any supermarket)
- Your scale and grinder
- 5 minutes
The Process
Step 1: Brew with tap water (2 minutes)
- Brew your usual recipe with tap water
- Same beans, same grind, same ratio, same technique
- Pour into Cup A
- Let cool for 2-3 minutes
Step 2: Brew with bottled water (2 minutes)
- Brew the exact same recipe with Ashbeck or Volvic
- Same beans, same grind, same ratio, same technique
- Pour into Cup B
- Let cool for 2-3 minutes
Step 3: Taste side-by-side (1 minute)
- Taste Cup A (tap water)
- Taste Cup B (bottled water)
- Go back and forth
- Notice the differences
Total time: 5 minutes. That's it.
What You'll Notice
If your tap water is the problem (and it probably is), here's what you'll taste:
Cup A (Tap Water) Will Taste:
- Flat: Dull, one-dimensional, lacking vibrancy
- Muted: Flavours are there, but suppressed
- Chalky or mineral-like: Unpleasant aftertaste
- Less sweet: Sweetness is masked
- Shorter finish: Flavours disappear quickly
Cup B (Bottled Water) Will Taste:
- Bright: Lively, vibrant, sparkling acidity
- Clear: Distinct, defined flavours
- Sweet: Caramel, honey, fruit sweetness emerges
- Complex: Multiple flavour notes you couldn't taste before
- Longer finish: Pleasant aftertaste that lingers
The difference is dramatic. It's like switching from a blurry photo to HD.
Why This Happens
UK tap water is typically:
- Too hard: 200-400 ppm TDS (ideal is 75-150 ppm)
- High alkalinity: Bicarbonates buffer acidity, making coffee taste flat
- Chlorinated: Chlorine adds off-flavours
What this does to coffee:
- High alkalinity neutralizes acids (goodbye brightness)
- Excess minerals interfere with extraction (goodbye sweetness)
- Chlorine adds chemical taste (goodbye clean flavours)
Ashbeck and Volvic work because:
- Low TDS (130-136 ppm — ideal range)
- Low alkalinity (doesn't buffer acidity)
- No chlorine (clean taste)
- Moderate hardness (helps extraction)
Result: Coffee tastes the way it's supposed to.
What to Do Next
You've done the test. You've tasted the difference. Now what?
Option 1: Use Bottled Water (Temporary Solution)
Pros:
- Immediate improvement
- No equipment needed
- Consistent results
Cons:
- Expensive (£1+ per litre = £30+ per month for daily coffee)
- Not sustainable (plastic waste)
- Inconvenient (carrying bottles home)
Best for: Short-term while you implement a better solution
Option 2: Carbon Filter (Better Than Nothing)
What it is: Brita-style filter jug
Pros:
- Affordable (£20-30 for jug + filters)
- Removes chlorine (improves taste)
- Reduces some minerals
- Convenient
Cons:
- Doesn't solve alkalinity problem (coffee still flat)
- Inconsistent (filter effectiveness degrades)
- Slow (takes time to filter)
Best for: Budget solution, better than tap but not ideal
Option 3: DIY Water Recipe (Best Long-Term Solution)
What it is: Create your own water using distilled water + mineral additions
The recipe (Barista Hustle Melbourne Water):
- 1 litre distilled or RO water
- 0.06g Epsom Salt (MgSO₄)
- 0.04g Baking Soda (NaHCO₃)
Result: ~100 ppm TDS, ~60 ppm hardness, ~40 ppm alkalinity (ideal for coffee)
Pros:
- Costs pennies per litre
- Consistent, repeatable
- Professional-level water
- Used by competition baristas
Cons:
- Requires 0.01g precision scale (£10-15)
- Requires distilled/RO water (£1-2 per 5L)
- Takes 5 minutes to prepare batch
Best for: Serious home brewers, long-term solution, best results
The Complete Water Chemistry Guide
The 5-minute test shows you what proper water does. But knowing how to fix your water permanently—with exact recipes, measurements, and troubleshooting—requires more detail.
In Pour-Over Perfection: Advanced Brewing Techniques, Chapter 2 covers water chemistry mastery, including:
- How to test your tap water (free and paid methods)
- The exact DIY water recipe with step-by-step instructions
- Where to buy ingredients in the UK (specific suppliers)
- UK-specific bottled water recommendations with mineral breakdowns
- How to remineralise distilled water with precision
- Troubleshooting water problems by taste
- Filter system recommendations (what works, what doesn't)
- How water interacts with different coffee origins and roast levels
Plus 14 other chapters covering grind theory, temperature profiling, advanced pouring techniques, systematic troubleshooting, and competition methods.
Get the complete 310-page guide for £19.99 →
Real-World Results
What happens when you fix your water:
Ethiopian coffee:
- Before: Flat, one-dimensional, vaguely fruity
- After: Bright blueberry, jasmine florals, complex, tea-like, vibrant
Colombian coffee:
- Before: Generic "coffee" taste, slightly sweet
- After: Caramel, brown sugar, hazelnut, balanced acidity, long finish
Kenyan coffee:
- Before: Sour, harsh, unpleasant
- After: Bright grapefruit, blackcurrant, wine-like, complex, lively
The same beans. The same brewing. Different water. Completely different coffee.
Common Questions
"Will this work with espresso too?"
Yes. Water matters even more for espresso because it's concentrated. The 5-minute test works with espresso—pull two shots, one with tap water, one with bottled water. Taste the difference.
"What if I don't notice a difference?"
Two possibilities:
- Your tap water is already good (rare in UK, but possible in some areas)
- Your palate needs training (do the test again in a week after practicing mindful tasting)
Most people notice an immediate, obvious difference.
"Can I use any bottled water?"
No. Most bottled waters are wrong for coffee:
- Evian: 345 ppm (too high, makes coffee taste chalky)
- Highland Spring: High alkalinity (makes coffee taste flat)
- Buxton: Too hard (interferes with extraction)
Use Ashbeck or Volvic specifically. They have ideal mineral profiles for coffee.
"Is this really necessary?"
Do the test and decide for yourself. If you taste a dramatic difference, then yes, it's necessary. If you don't, then no.
But coffee is 98% water. Ignoring water quality is like buying a £500 grinder and using stale beans. It doesn't make sense.
Your Next Steps
Today:
- Buy one bottle of Ashbeck or Volvic (£1 from any supermarket)
- Do the 5-minute water test
- Taste the difference
This week:
- If you noticed a difference, decide on a solution (bottled, filter, or DIY)
- Read the complete water chemistry chapter in Pour-Over Perfection
- Implement your chosen solution
Next month:
- Enjoy dramatically better coffee
- Wonder why you didn't fix this sooner
Water is 98% of your coffee. Fix it.
Get the complete water chemistry guide →
This post is an extract from Chapter 2: Water Chemistry Mastery in Pour-Over Perfection. The full chapter includes detailed water testing methods, exact DIY recipes, UK supplier lists, and everything you need to fix your water permanently.