WATER TEST – Which Water Is Best for Brewing Coffee?

In this article, we’ll explore what kind of water you should use to brew coffee if you truly care about quality. Great coffee starts with the beans — but it’s finished with the water.

Why Is Water So Important in Coffee Brewing?

If you think about it, a cup of coffee is made up of roughly 94–98% water. With instant coffee, the proportion of dry ingredients is obviously higher; with brewed coffee, it’s lower. The quality of the coffee beans, the roast level, and the grind size can only truly shine if the water is able to properly extract the aromas. That’s why there’s a well-known saying among coffee professionals: you can’t make good coffee with bad water.

Water’s ability to dissolve compounds influences not only flavor, but also acidity, body, and even the coffee’s aftertaste. On top of that, the type of water you use in your coffee maker matters as well — water that’s too hard can damage your machine over time.

The Impact of Water on Coffee

Many people don’t even realize what level of water hardness their coffee is brewed with. The minerals present in water determine its hardness — and, at the same time, the flavor of the coffee you end up drinking.

The most suitable water for brewing coffee has a pH level of around 7.

Hard Water

If you brew coffee with water that’s too hard, fewer of the compounds that create aroma are extracted from the coffee. As a result, the coffee tastes dull and underdeveloped.

If you can’t change the hardness of your water, you can adjust either the amount of ground coffee (use more) or the grind size (grind finer). This can help produce a more aromatic cup, although brewing with hard water is still far from ideal.

What does hard water cause in the long run?

• Scale buildup inside the coffee machine
• Poor heat transfer (leading to weak extraction)
• Low-acid, “flat” coffee flavor
• Machine malfunctions and expensive repairs

For this reason, most baristas aim for water hardness well below 200 ppm (mg/L as CaCO₃) to avoid dull flavors and scale buildup.

Soft Water

If the water used for brewing coffee is too soft, compounds can be extracted from the grounds that make the coffee taste bitter. This happens because the coffee becomes over-extracted.

Problems caused by overly soft water:

• The coffee tastes bitter and bland
• Excessive acidity and sometimes almost “metallic” notes appear
• It can cause corrosion in certain coffee machines

Baristas do not recommend 0 ppm water (distilled water), as it makes coffee almost completely flavorless.

The Role of Water in Coffee Extraction

During coffee brewing, water plays several crucial roles:

• It acts as a solvent, extracting flavors, aromas, and oils from the coffee grounds.
• It creates balance, determining whether a cup of coffee tastes overly acidic, excessively bitter, or well-rounded and harmonious.
• It transfers heat, ensuring the optimal temperature needed for proper extraction.
• It interacts with the mineral ions in the coffee grounds, which means the mineral composition of the water directly affects how well the coffee’s flavors are expressed.

According to coffee science and industry standards, good brewing water should be neither too soft nor too hard. Ideally, it should meet the following criteria:

• Total hardness: 50–150 mg/L (ppm) as CaCO₃
• pH: around 7 (neutral)
• TDS (Total Dissolved Solids): 100–150 ppm
• Calcium-to-magnesium ratio: magnesium enhances flavor extraction, so water should not be overly calcium-dominant

Water Test

An informal tasting experiment with eight participants was carried out to see which type of water results in the best-tasting coffee.

At the beginning of the test, the eight participants were first evaluated to identify those who were not able to reliably distinguish flavors. During the tasting, these individuals gave different scores to coffees brewed with similar waters, even though the water used was the same. As a result, they were excluded from the remainder of the test.

The participants who passed this initial screening went on to evaluate coffees brewed with the following types of water:

• high-mineral-content water
• lower-mineral-content water
• tap water
• water filtered using a kitchen pitcher-style water filter
• water filtered using an under-sink kitchen water filtration system

Water Test Results

The water test confirmed the common claim that coffee brewed with hard water is less flavorful than coffee made with softer water.

Participants gave the lowest scores to coffees brewed with high-mineral-content hard water as well as to coffees made with tap water.

How to Test Your Water at Home (Water Testing Tips)

If you want to know whether your household water is suitable for brewing coffee, there are several simple methods you can try:

1. TDS Meter

A digital TDS meter shows how many dissolved minerals are present in your water.
Ideal TDS for coffee: 100–150 ppm.

2. Water Hardness Test Strips

• 0–71 ppm: very soft water
• 71–142 ppm: ideal for coffee
• 142–249 ppm: moderately hard water
• Above 249 ppm: too hard → scale buildup and poor extraction

3. Boiling Test

Boil a small amount of water and observe the results:

• If a milky white residue remains, the water is hard.
• If there is little to no visible residue, the water is soft.

Over time, any kettle will eventually develop limescale, but the speed at which this happens matters. If your kettle shows scale buildup after just a few uses, it’s a strong sign that your tap water is hard.

4. Taste Test – The Easiest Water Test

Fill two glasses: one with tap water and the other with filtered water. If the filtered water tastes better, your tap water is likely hard. Brewing coffee with filtered water will noticeably improve the taste as well.

How Different Types of Water Behave When Brewing Coffee

1. Tap Water

Pros: Convenient, inexpensive, contains natural minerals
Cons: Often too hard or chlorinated

The presence of chlorine can severely affect the taste of your coffee, resulting in a bitter, flat cup.

2. Bottled Mineral Water

Not the best choice for brewing, as even low-mineral bottled water often has a higher ppm than regular tap water. Too many dissolved minerals can overwhelm and mute the coffee’s delicate flavors.

3. Pitcher-Filtered Water

In most households, this provides the best results. It reduces hardness, improves taste, and removes chlorine.

4. Under-Sink Filtration System

Provides years of trouble-free operation for your coffee maker and consistently high-quality water for brewing.

5. RO (Reverse Osmosis) Water

Water produced with RO technology is usually too soft for optimal coffee extraction. Baristas often use it only if they reintroduce minerals afterward to balance the water.

Coffee Machine-Friendly Water – How to Protect Your Machine

One of the biggest enemies of coffee makers is limescale.

With hard water:

• Pipes can become clogged
• Heat transfer efficiency decreases
• Energy consumption rises
• The machine’s lifespan drops significantly

For this reason, most manufacturers recommend using softened or filtered water. It’s often worth investing in some kind of water filtration system to keep your coffee maker in top condition.

DXN Ganoderma Coffee – When Coffee Quality Matters as Much as Water

If you want to pay attention not only to the quality of your water but also to the quality of your coffee, choose healthy coffee options. I recommend DXN Ganoderma coffees, which, thanks to the ganoderma mushroom they contain, help alkalize the body. Personally, they’ve worked really well for me. 🙂

The ganoderma mushroom:

• Reduces acidity
• Supports the immune system
• Aids digestion
• Provides a natural, caffeine-friendly experience

Coffee made with good water and high-quality ganoderma coffee delivers a completely different experience — both in taste and in its effects.

More Tips for Perfect Water and Coffee

1. Always Use Fresh Water

Stagnant water loses oxygen, which can result in dull flavors in your coffee.

2. Water Temperature Matters

• Ideal extraction: around 190°F (≈90°C)
• Too hot: burnt taste, over-extracted coffee
• Too cold: sour, under-extracted coffee

3. Experiment with Different Types of Water Using the Same Coffee

This is the most visual and effective water test. You’ll see firsthand how much the taste of your coffee can change depending on the water you use.

Summary: What Water to Use for Coffee

• pH: around 7 (neutral)
• TDS: 100–150 ppm
• Moderately soft water (≈71–142 ppm, formerly 4–8 °dH)
• Filtered, but not completely mineral-free
• Chlorine-free

Using water with these characteristics will not only improve the flavor of your coffee but also extend the lifespan of your coffee maker.