The 10 Possible Reasons For Sour Coffee (How To Fix It)

Last Updated on May 26, 2022 by John Moretti

A mouthful of sour coffee in the morning might shock you awake, but so does dousing yourself with a bucket of cold water. Some people can throw enough sugar at the problem that it doesn’t bother them anymore. But not everyone is eager to see their dentist on a more frequent basis. So why does sour coffee occur, and how do we fix it?  

Sour coffee can happen for many reasons:

  1. Aging machine
  2. Beans too fresh
  3. Coarse ground
  4. Dirty machine
  5. Poor extraction
  6. Poorly roasted beans
  7. Not using enough water
  8. Hipster joint
  9. Stale beans
  10. Wrong brew time

The fix can be anything from cleaning your machine to changing your grind. 

sour coffee

Look, we can all go out and buy a pod maker and achieve a consistent cup pod by pod. But where is the fun in that? Besides, there is so much potential when brewing your own coffee. Also, the problem may be an easy one to fix. It’s all about going through the options and pinpointing the likely culprit. 

10 Reasons Coffee Tastes Sour And How To Avoid It

Brewing coffee is a science. Like any science experiment, getting it exactly right requires troubleshooting, using the time-honored process of trial and error. To assist your quest to eliminate sour coffee from your life, we’ve listed ten potential reasons and how to fix them. Wishing you a better brew ahead. 

1. Aging Machine: Fixing Sour Coffee

how to make tea using an espresso machine

The Problem: So old faithful has been filling your house with the smell of coffee every morning for the past twenty years. Which is a lovely story, but the machine is tired, and your brew tastes like it. 

The Fix: If you have tried everything listed below and nothing is working, then the only thing left to do is upgrade your tired coffee maker. If you are not 100% convinced it’s your aging technology that’s the problem, try a French press or beg a friend to let you try their machine first. But sometimes, the truth is that the old faithful is ready for retirement. 

2. Beans Too Fresh: Fixing Sour Coffee

The Problem: Fresh is best unless your coffee beans are less than a week old. Recently roasted beans give off carbon dioxide for 3-5 days, sometimes as long as a week. 

The Fix: Having fresh beans is wonderful but think of them as a nice bottle of red wine: you need to let them breathe. So let your fabulous fresh roasted beans have a week to exhale before you put them to work. 

3. Coarse Ground: Fixing Sour Coffee

Coarse ground coffee

The Problem: Your beans are too coarse for your chosen coffee brewing method, leaving you with a sour aftertaste. 

The Fix: You’ve got two choices: change the brewing method to fit the grind, or grind your beans to fit the brewing method.  

4. Dirty Machine: Fixing Sour Coffee

The Problem: You fear building up so much that all you do is rinse your machine. Thus, your water reservoir, grinder, and filters are started to become the coffee equivalent of a high school locker room. Ick. 

The Fix: Wash your equipment about once a week. Some machines have a self-cleaning function, which makes it easy. Others, such as a French press, can often be popped right into the dishwasher. 

For grinders:

  • Toss in some dry, uncooked rice
  • Run the grinder
  • Dump the fine white powder into the bin
  • Then wipe out the unplugged grinder with a damp cloth

5. Poor Extraction: Fixing Sour Coffee

pour extraction

The Problem: Poor extraction, either over or under, produces sour coffee. 

The Fix: Your extraction method needs assessing and tweaking. 

Under extraction can be fixed by buying better quality beans or grinding your coffee less finely. 

Over extraction happens when the coffee sits in water for too long. For example, if you forgot about the coffee sitting in the French press while you sang in the shower, you might be in for a really sour mouthful. 

6. Poorly Roasted Beans: Fixing Sour Coffee

Ohoto of medium roast and light roast coffee

The Problem: Many new to roasting their own beans will under roast them out of fear they’ll burn their beans. The problem is under roasted beans can make a sour brew. 

The Fix: Longer roast provides a richer flavor. So try to find where your sweet spot is. 

If you are buying beans, talk to the roaster and see if they have a darker roast for sale. 

Another fix can be using a coarser grind. Yes, too coarse a grind can also produce sour coffee. But brewing is like chemistry; it’s a tweak here, tweak there until you’ve got it just right. 

7. Not Enough Water: Fixing Sour Coffee

not enough water

The Problem: You are not adding the right amount of water. 

The Fix: Add more water. 

8. Hipster Joint: Fixing Sour Coffee

modern coffee shop

The Problem: You are having a midlife crisis and frequent Hipster coffee joints, unaware that sour (tart) coffee is a trend. 

Yes, really. 

The Fix: Either get hip and embrace the sour (tart) taste, add sugar (or agave, depending on the establishment), or find a new coffee hangout that caters to your palate. Even better, brew your own. 

9. Stale Beans: Fixing Sour Coffee

The Problem: That bag of coffee you found in the back of the pantry from Christmas two years ago? It’s stale, and that can make coffee sour.

The Fix: You need new beans to brew. Perhaps use the old ones for an art project or compost. Roses love the nitrogen boost a few coffee grinds can provide. Some people also use ground coffee to make an excellent skin scrub. 

10. Wrong Brew Time: Fixing Sour Coffee

brewing chemex coffee

The Problem: Your brew time is too short or too long. One of the drawbacks of not using pods or an automated machine is that the potential for user error is high. On the other hand, once you’ve found the perfect brew method, you’ll blow all those pod capsules out of the mugs. 

The Fix: You need to adjust your brew times until you’ve got it right. When it comes to sour coffee, it is typically too short of brew time. Which makes sense since we’re all in a hurry and want our caffeine jolt now. So put yourself on a timer and start brewing a minute longer, and then a minute more, until you’ve found the perfect brewing time. 


Sour coffee is a bummer, but as life problems go, at least this one is fixable. So give your old beans to the roses, clean your machine, and adjust your grind. With these simple tweaks, a delicious brew will soon be filling your favorite mug.