Understanding Tap Water Quality
When we talk about making better coffee, most of the attention usually goes to the beans, grinder and brewing method.
But there’s another ingredient making up most of what’s in your cup: water.
So, can you use ordinary tap water to brew coffee?
Absolutely – but the quality of that water matters.
Tap water varies from one area to another, including across South Africa. Its mineral content, pH and treatment can all influence the way your coffee tastes. Even if your tap water tastes perfectly fine on its own, it can still affect extraction once it meets your coffee grounds.
Ideally, brewing water should be reasonably balanced. Water that is very hard can contribute to mineral buildup and affect extraction, while water that is too soft may produce a less complex or balanced cup.
The Specialty Coffee Association has guidelines around brewing-water composition, highlighting the importance of factors such as mineral content and pH. Getting that balance right can help your coffee taste more like the coffee you intended to brew, rather than letting the water dominate the cup.
How to Assess Your Tap Water
Before buying special coffee water or investing in a complicated setup, start with the basics.
Have a glass of your tap water and actually taste it.
Does it have a strong chlorine smell? Does it taste unusual or metallic? Are there any other flavours or odours that you wouldn’t want in your coffee?
If your drinking water already tastes unpleasant, there’s a good chance those characteristics won’t magically disappear when you brew coffee with it.
You can also get a rough idea of your water hardness using a simple home test. Fill a bottle with tap water, add a few drops of dishwashing liquid and shake it.
If it foams easily, your water is probably not extremely hard. If it produces very little foam, it may contain a higher level of minerals associated with hard water — worth knowing before you next brew a French press, since scale builds up fastest in equipment that heats water repeatedly.
This is only a basic indication rather than a precise scientific measurement, though.
For a more accurate picture, inexpensive water-testing kits can provide additional information. You can also use equipment that measures total dissolved solids, commonly referred to as TDS, to get a better understanding of what’s in your water.
Conducting a Taste Test
One of the best ways to find out whether your tap water is affecting your coffee is surprisingly simple: make two cups.
Brew the same coffee using your normal tap water, then brew another cup using high-quality water designed or selected specifically for coffee.
Taste them side by side.
You may notice differences in sweetness, acidity, body and overall flavour. Or you may find that your tap water works perfectly well with your favourite beans.
Either way, the comparison gives you a much better answer than simply assuming your tap water is good or bad for coffee.
For coffee lovers who enjoy experimenting at home, this can be a surprisingly interesting little test. You may discover that the water coming out of your kitchen tap has more influence on your coffee than you expected.
Challenges of Using Tap Water
Taste isn’t the only thing to consider.
If your tap water contains a high level of minerals, those minerals can gradually build up inside your coffee equipment. This is known as scale.
Coffee machines, kettles and automatic brewers with heating elements can be particularly affected because water is repeatedly heated inside the equipment.
Over time, scale can affect how your equipment performs and make cleaning more difficult.
Regular cleaning and descaling can help keep your coffee equipment working properly, especially if you live in an area with hard water.
It’s worth checking your machine’s cleaning instructions and following the recommended descaling routine rather than waiting until you can see a problem.
Improving Tap Water for Brewing
If you’ve tested your tap water and decided it could be better, you have several options.
1. Water Filtration
A good-quality water filter is one of the simplest places to start.
A filter jug or an inline tap filter can reduce certain impurities and improve the taste of your water. Depending on the type of filter you use, it can also reduce some of the minerals that contribute to hardness.
Filtered water can make a noticeable difference to coffee, particularly if your tap water has a strong taste or contains a high level of minerals.
2. Addressing Hard Water
Very hard water can be more challenging to manage.
Standard carbon or ion-exchange filters may not always reduce mineral hardness enough for your particular needs. Some coffee-water approaches involve adjusting the water chemistry with small quantities of substances such as food-grade citric acid, lemon juice or vinegar.
The idea is to counter some of the carbonate compounds that can affect the balance of acids in coffee.
However, this is an area where a little caution is worthwhile. Adding ingredients to brewing water without knowing your water chemistry can easily make things more complicated, so testing your water first is a better approach than simply adding something and hoping for the best.
3. Alternative Water Sources
Another option is bottled spring water.
Some spring waters have a mineral profile that works well for coffee, although not every bottled water is the same. If you go this route, checking the mineral information on the label can help you choose more deliberately.
Distilled water, meanwhile, generally isn’t the best choice for brewing coffee on its own because it contains very few minerals. Minerals play an important role in coffee extraction, so completely mineral-free water can produce a less satisfying cup.
Final Thoughts
Water might not be the most exciting part of making coffee, but it can have a surprisingly big impact on the final cup.
If your tap water tastes good and has a suitable mineral balance, there’s no reason you can’t use it to brew excellent coffee. If you notice strange flavours, excessive scale or inconsistent results, your water may be worth investigating.
Start with something simple: taste your tap water, check its hardness if you can, and compare a cup brewed with your usual water against one made with coffee-friendly water.
You may find that your tap water is perfectly fine. Or you might discover a relatively simple change that makes your morning coffee noticeably better.
Either way, experimenting is part of the fun.
Join The Coffee Blog Community
At The Coffee Blog, we’re interested in all the little details that can make a difference to your daily cup, from the beans and grinder to the brewing method and, yes, even the water.
If you enjoy learning more about coffee, take a look at our guide to 20 coffee brewing methods for brewing tips, coffee science, flavour guides and plenty more from the world of coffee.
Because sometimes, improving your coffee doesn’t start with buying better beans.
It starts with looking at what you’re putting them into.
