Last Updated on May 18, 2022 by John Moretti
I cannot overstate how much I love my Moka pot. It provides a surprisingly cheap solution for consistently good coffee (with some practice, of course). But, it can be equally confusing and annoying when your Moka pot starts leaking, forcing you to restart the brewing process and waste good coffee.
There are six common reasons your Moka pot could be leaking:
- Not using the correct size coffee grind
- Filling the filter basket with too much coffee
- Tamping the coffee in the basket
- Overfilling the water reservoir
- Not cleaning your Moka pot correctly, and
- Using a Moka pot with an old and worn gasket
It may be frustrating watching that coffee your system is craving, leaking from every crevasse, but fortunately, the process of fault-finding and fixing is quick and easy.
1. Use The Right Coffee Grind
Knowing what type of coffee grind (fine or coarse) to use is crucial for brewing any coffee, from espresso to cold brew. Espresso, for example, requires a very fine grind to allow for as much ‘surface area’ contact with the water.
However, a fine grind also leaves very little room for the water to pass through the coffee. While this is not a problem when using an espresso machine that pulls shots at 9 bars, it is a stumbling block for a Moka pot.
Moka pots only produce between one and two bars of pressure. With its limited space between each particle, fine-grind coffee makes it difficult for the water to pass through at those pressures.
If this happens, your pot will build up pressure in the reservoir as the water boils and escapes through the pressure valve.
You may get a few drops of brewed coffee in the process, but chances are that it won’t taste great because of the extra time it took for the water to worm its way through the basket.
To fix this problem, you need to use a relatively coarse grind. If you are buying pre-ground coffee, make sure it is a coarse grind, but I would advocate that you get yourself a decent burr grinder at home to control this vital part of the brewing process.
You will also get a better cup of coffee using fresh grounds.
2. Do Not Overfill The Basket
One trap that I had fallen into many times when I learned how to use my Moka pot was overfilling the basket with coffee.
I used to overfill the basket, ensuring no gaps in the grind and heaping the coffee. This is a mistake.
Overfilling the filter basket has much of the same effect as using fine-grind coffee. In this case, the coffee becomes compressed between the basket and the filter. It expands when water is introduced, compressing it even more.
In this case, you will see your pressure release valve desperately sputtering to try and get rid of the pressure. If you managed to properly overfill the basket and the pressure valve can’t keep up, you will likely start seeing leaking from the gasket seal as well.
Don’t expect any salvageable coffee from this epic fail.
Don’t be tempted to overfill the basket. Simply fill it so that it sits flush with the upper rim of the basket. Then, you can use the back of a knife (or your finger if you’re like me) to scrape away excess coffee.
If there are gaps in the coffee, it’s OK! Just leave them, brew your coffee and enjoy.
3. Never Use A Coffee Tamp
I know, it looks so professional when your friend with his expensive espresso machine tamps his coffee, squashing it into a perfect puck before he brews it. But, please, I beg you, don’t be tempted to do this with your Moka pot.
Tamping is the third and biggest pressure-related mishap of Moka pot brewing. As mentioned earlier, your Moka put produces 5 to 9 times less pressure than an espresso machine, and you need A LOT of pressure to force water through a tamped coffee puck.
Tamping your coffee is a sure-fire way to end up with leaks or even damage the structural integrity of your Moka pot. Just don’t do it.
4. Don’t Overfill The Water Reservoir
Another reason for seeing leaking out of the pressure valve is overfilling the water reservoir.
Having too much water in your pot means there isn’t enough room to accommodate the pressure build-up as the pot was designed. This will force the excess water out of the pressure valve or between the screw threads.
It could also ruin the brew, making it weaker than it ought to be.
To avoid overfilling, check inside the reservoir for a max-fill line. If you don’t see a line, you can use the rule of thumb and fill it up below the pressure release valve.
5. Clean Your Moka Pot Properly After Every Use
Cleaning your equipment is an essential step in the coffee-making process. It not only ensures that your Moka pot is in good working order but also removes the “old-dirty-stale” coffee flavor from your brew.
Not cleaning your Moka put properly could leave blockages in the filter or pipe, adding to the pressure. You may also have grounds of coffee lodged between screw threading, which will prevent a proper seal and result in leaking.
Here is a video showing you how to properly scrub your Moka pot:
6. Replace Parts That Are Old And Tired
If, after following the previous steps, your Moka pot still leaks around the seal, you may have to replace the gasket.
The gasket is the O-ring seal (often made of a rubber compound) that sits in the grove where the coffee collector (or upper chamber) screws onto the water reservoir. If this gasket is old, it becomes brittle and starts to perish, cracking in the process.
The cracks compromise the quality of the seal and allow a path for water to escape when pressure builds up in the reservoir.
One of my favorite things about a Moka pot is that maintenance is painless and relatively cheap. Spares are readily available and, for just about any fix, the process typically involves a “just pop the new one in” approach.
Get hold of a replacement gasket, which can be bought in packs containing multiple units. Then, using an object like a knife, remove the old gasket (preferably without also removing your finger) and then pop the new one into place.
Similarly, the filter also has a life span, and if it becomes worn, it may become permanently blocked or cracked. A clogged filter could cause a pressure leak, while a broken one will allow the water to flow too quickly and result in a mess in the collector.
There are six typical causes for a leaking Moka pot. Using the wrong grind, too much coffee, or tamping the coffee will prevent the water from flowing through the coffee, causing too much pressure and leaking. Using too much water or using a dirty Moka pot can also lead to leaking.
Finally, you may need to replace some of the expendable parts on your Moka pot to keep brewing smoothly and prevent it from leaking. Fortunately, these parts are readily available, cheap, and easy to replace. With some practice and good fault-finding, you will be brewing great coffee in no time.