Why Water Matters

Espresso is roughly 90% water by weight. The minerals in your water directly affect extraction and flavour. They also determine whether your machine develops scale buildup, which is the number one cause of espresso machine failure.

Getting water right is not complicated, but ignoring it can ruin both your shots and your equipment.

The Problem with Tap Water

Tap water quality varies enormously by location. Some areas have soft water with almost no minerals, others have extremely hard water loaded with calcium and magnesium. Neither extreme is ideal for espresso.

Hard Water (High Mineral Content)

Hard water extracts aggressively. The high concentration of calcium and magnesium ions pulls more soluble compounds from the coffee, which can lead to over-extraction and harsh, bitter flavours.

More critically, hard water causes limescale buildup inside your machine. Scale accumulates in the boiler, pipes, solenoid valve and group head. Over time it restricts water flow, reduces heating efficiency and can eventually block the system entirely. Descaling regularly helps, but prevention is better.

Signs your water is too hard:

White chalky deposits around your kettle, shower screen or steam wand
Bitter, harsh shots even with proper technique
Machine running slower over time
Scale flakes appearing in your cup

Soft Water (Low Mineral Content)

Soft water under-extracts. Without enough minerals to drive extraction, shots taste thin, flat and sour. The espresso lacks body and sweetness. Very soft water (like pure distilled or reverse osmosis water) also lacks the buffering capacity to balance the natural acidity of coffee, making shots taste sharp.

Extremely soft water can also be corrosive to copper boilers and brass fittings over time.

Signs your water is too soft:

Thin, sour shots that do not improve with finer grinds
Espresso with no body or sweetness
Flat, lifeless flavour

What Makes Good Espresso Water

The Specialty Coffee Association recommends water with these characteristics:

Parameter	Target Range
Total hardness (as CaCO₃)	50–175 ppm
Alkalinity (as CaCO₃)	Around 40 ppm
pH	6.5–7.5
Total dissolved solids (TDS)	75–250 ppm
Chlorine	0 ppm

You do not need to hit these numbers exactly. The key principles are:

Some minerals, but not too many. Enough magnesium and calcium to drive extraction, not so much that you get scale.
Some alkalinity to buffer acidity. This prevents the shot from tasting sharp.
No chlorine. Chlorine tastes terrible in coffee and damages machine seals.

Your Options

Option 1: Carbon Filter (Easiest)

A basic carbon water filter (like a Brita jug) removes chlorine and some impurities but does not significantly change mineral content. If your tap water is already in a reasonable hardness range (50 to 175 ppm), a carbon filter might be all you need.

Pros: Cheap, simple, removes chlorine and off-flavours.

Cons: Does not reduce hardness. If your water is very hard, you will still get scale.

Option 2: In-Tank Filter (Most Common)

Many espresso machines accept in-tank filter cartridges that soften the water and remove impurities. BWT, Brita Intenza and similar brands make cartridges specifically designed for coffee machines.

Pros: Fits inside the water tank, set and forget. Reduces hardness and removes chlorine. Designed for espresso.

Cons: Needs replacing every 1 to 3 months depending on water hardness. Adds ongoing cost.

Option 3: Third Wave Water or Mineral Packets

Start with distilled or reverse osmosis water (zero minerals) and add a mineral packet designed for espresso. Brands like Third Wave Water provide pre-measured sachets that create water with ideal mineral content.

Pros: Precise control over mineral content. Eliminates scale risk entirely. Consistent from batch to batch.

Cons: Requires buying distilled water. More effort. Can feel excessive for casual users.

Option 4: DIY Mineral Water

Mix distilled water with small amounts of magnesium sulphate (Epsom salt) and sodium bicarbonate (baking soda) to create custom espresso water. Recipes are available from the specialty coffee community.

A common simple recipe: add 0.3g of Epsom salt and 0.1g of baking soda per litre of distilled water.

Pros: Very cheap once you have the ingredients. Full control.

Cons: Requires a precision scale and some experimentation.

The Practical Approach

For most home baristas, here is the simplest path:

1.Test your tap water. Buy TDS meter for a few dollars and check your total dissolved solids. If it reads between 75 and 200 ppm, your water is probably fine with a basic carbon filter.

1.If your water is very hard (above 200 ppm): Use an in-tank filter cartridge or switch to filtered water from a jug filter designed to reduce hardness.

1.If your water is very soft (below 50 ppm): Add minerals. Third Wave Water sachets are the easiest method.

1.Descale regularly regardless. Even with filtered water, descale your machine every 2 to 3 months as a preventive measure. Follow your machine manufacturer's instructions.

How Water Affects Flavour

The mineral composition of your water subtly but noticeably changes how your espresso tastes:

Magnesium enhances extraction of fruity, complex flavour compounds. Water with more magnesium tends to produce brighter, more nuanced shots.
Calcium contributes to body and mouthfeel. It produces a heavier, rounder cup but can mute delicate flavours.
Bicarbonate (alkalinity) buffers acidity. Too little and shots taste sharp. Too much and they taste flat and chalky.

If you are already dialling in well and want to push your espresso further, experimenting with water composition is one of the most impactful changes you can make. It is often more noticeable than switching grinders.

Protecting Your Machine

Regardless of flavour preferences, protect your machine from scale:

Descale on schedule. Every 2 to 3 months for home use, more often with hard water.
Use the right descaler. Citric acid-based descalers are gentle and effective. Avoid vinegar — it is harder to rinse completely and can leave residual flavours.
Flush after descaling. Run at least two full tanks of clean water through the machine after descaling to remove all traces of the descaling solution.
Check your steam wand. Scale often builds up inside the steam wand tip. If steam pressure drops, soak the tip in descaler overnight.

Key Takeaways

Your espresso is 90% water — its mineral content directly affects flavour and extraction
Hard water causes scale buildup and bitter shots. Soft water causes flat, sour shots
Aim for 75 to 175 ppm total dissolved solids
A carbon filter or in-tank cartridge handles most situations
Descale every 2 to 3 months regardless of water type
Removing chlorine is the single most impactful water improvement

Water quality for espresso: why it matters more than you think