A sputtering, bubbling, hissing, or spitting moka pot is more than just an annoyance. Moka pots are full of pressurized steam and hot water, so any sputtering is potentially dangerous.
A sputtering moka is caused by too much pressure inside your moka pot. This may be because you’ve got the heat on too high, you’ve compressed your beans too much, or your moka pot isn’t sealed properly due to dirt or wear and tear. You can usually fix a sputtering moka by taking it apart and cleaning it, although in some cases you may need to replace the seal.
In this article, we’ll cover some common reasons your moka pot may be sputtering, and look at some ways you can fix it.
What Causes a Moka Pot to Sputter?
A sputtering moka pot is caused by excess pressure inside your moka, an incomplete seal between the chambers, or too many beans in the extraction chamber.
The only sound you should hear from your moka pot is a gentle gurgling once your coffee is ready. If you’re hearing spitting or sputtering, it means there’s either too much pressure inside your moka, or you don’t have a perfect seal between each of the chambers of the moka pot and some steam is escaping.
Let’s take a look at each of these issues in more detail before we go over how to fix them.
1. Too Much Pressure
Pressure is an essential aspect of the moka brewing process. As the bottom chamber heats up, expanding air forces the hot water up through the spout, through the coffee grounds where extraction takes place, and up into the top chamber where your finished coffee is collected.
When too much pressure builds up inside the moka pot, hot water and steam may sputter and bubble out of the top of the pot, through any weak points in the rubber seal, or through the safety valve that’s present on all moka pots.
You can help reduce the pressure inside the pot by reducing the temperature.
2. Imperfect Seal Between the Moka Chambers
Since the inside of a moka pot is pressurized when it’s in use, but the pot also has to be able to come apart to fill it up, the design relies on a strong, airtight seal to prevent all the pressure from escaping.
Each moka is designed slightly differently, but the most common design is for the chambers to be screwed together by hand with a metal thread, and sealed with a rubber gasket.
An imperfect seal can be caused by wear and tear of the rubber gasket, dirt on or around the seal or in the thread, or the chambers not being screwed together tightly enough.
3: Too Much Coffee
In a moka pot, extraction occurs in the central chamber, where the water is forced up from the bottom chamber into the grounds and then up into the top chamber when it’s ready.
Coffee grounds expand as they soak. If your moka pot is overfilled (or the grounds are tamped down too tightly) the water will spit and sputter as it tries to escape the bottom chamber but has nowhere to go.
This may also result in acidic, under brewed coffee, or raw coffee grounds ending up in the upper chamber.
How To Fix a Sputtering Moka Pot
Now that we know what causes a moka pot to sputter, let’s take a look at some simple tips to fix it.
1. Turn Down The Heat
Although you need to heat the water in the bottom chamber, too much heat can cause excess pressure to build up, which forces the water through the grounds too quickly, resulting in sputtering and insufficient extraction.
Reducing the heat on the stove will help pressure build slowly and ensure you don’t end up with under brewed coffee.
2. Clean Around the Threads and Seals
Since moka pots operate using pressure, any stray coffee grounds or other pieces of dirt that get stuck in the metal threads can prevent an air-tight seal from forming and cause your moka to sputter and spit.
Before you close the coffee maker, clean all the metal surfaces with a damp cloth to remove any dirt or grit that would break the seal. The most important parts to check are the metal threads where the top and bottom screw together, the top lip of the cup, and the area around the rubber gasket.
3. Check The Funnels are Clear
On the inside of your moka, there are two funnels. One connecting the bottom chamber to the coffee grounds, and the other connecting your grounds to the collector at the top.
The way the moka pot works is that pressure builds in the lower pot, and expanding air pushes the water up through the two spouts, through the coffee grounds.
Any grounds or beans clogging either of the two funnels in a moka pot can cause sputtering and spitting as the water tries to push its way past any blockages. Check the insides of the funnels for any blockages to help reduce sputtering.
It’s easy to overlook hard-to-reach spots when cleaning your coffee machine. Check out my guide to cleaning your coffee machine using vinegar.
4. Replace The Rubber Seal
If you’ve already cleaned your moka pot and you’re still seeing water or steam sputtering out through the sides, you probably need to replace the rubber gasket that provides the seal.
These rubber gaskets are just small, circular pieces of rubber that provide a better seal than metal-to-metal could. They wear out over time, they are super cheap, it’s no big deal to replace them.
Amazon has a seal for all of the most popular brands. Check out the available seals here and pick the one that matches your moka pot.
5. Don’t Overfill Your Moka
When you’re adding your ground beans to your moka, don’t fill up the filter cup right to the brim. It’s unnecessary and can cause sputtering.
According to Bialetti, you should only loosely fill the filter cup, and avoid tamping your coffee down as it makes it harder for the water to pass through.
6. Buy New Moka Pot
Your final option to fix a sputtering moka pot is to replace it with a non-sputtering one. Over time, the various components of your pot suffer from general wear-and-tear, which can lead to sputtering.
If you’re considering a new coffee maker to replace your old sputtering moka pot, check out my Home Espresso Machine Guide for some tips on picking up a new coffee maker.
Does a Sputtering Moka Pot Affect the Taste of Coffee?
If your moka pot is sputtering, it means somehow, somewhere the water and steam are escaping instead of passing through your coffee.
Depending on the cause, a sputtering sound coming from your moka pot may mean it’s losing heat or pressure, which could result in a sour-tasting coffee.
Is a Sputtering Moka Pot Normal?
External sputtering is not normal for a moka pot. If you see any water or steam escaping from your moka as you use it, you either have too much pressure or there’s a problem with your seal.
Why Does my Moka Pot Gurgle?
It’s normal to hear a gurgling noise coming from your moka pot once it’s ready. This should be around 6 minutes after you turn it on. When you hear the gurgling noise, make sure to take it off the heat to avoid burning your coffee.
If your moka pot is sputtering, it usually means there is too much pressure inside, or that you don’t have a good enough seal to hold the pressure in.
An imperfect seal may be caused by stray coffee grounds or other dirt, so cleaning your moka pot is sometimes all it takes to stop the sputtering.