If the safety valve opens you’ll most likely hear a ‘pop’ sounds and see steam hissing from the base of your machine. This is nothing to worry about, as the safety valve is designed to open in this way if the water from the boiler isn’t able to pass through the coffee. The safety valve is at the base of your machine, on the side of the boiler.
There are three main reasons why the safety valve may open:
1. The heat setting is too high
If the machine is heated too quickly, then the pressure will also build too quickly and the safety valve will open before the machine has finished producing an espresso. You should be heating your machine so that it starts to produce an espresso between 3 and 6 minutes after you start heating it. If it’s faster than this, turn the heat setting down a little.
2. The coffee is ground too fine
If the safety valve is opening after heating the machine for more than 3 minutes, it’s most likely a result of your coffee being ground too fine. You may find that you’re getting only a small amount of espresso in the portafilter. Simply grind the coffee more coarsely so that the water can pass through the coffee more easily. This is the most common reason why the valve opens, so we always recommend starting with a coarser grind and gradually dialling it down so that you reach a 25 to 30 second extraction time.
A good way to test this is to run a cycle without any coffee in the basket. If water appears in the portafilter we know that the coffee was causing the issue and grinding more coarsely should resolve it. If water doesn’t appear, move on to step 3.
3. There’s a blockage
It’s rare, but it’s possible for the heat exchanger coil or boiler pipe to become blocked, most commonly in hard water areas where limescale is a problem. Try running the machine with no coffee in the basket; if the safety valve still opens, then you have a blockage. If that’s the case, this article can help – you can skip straight to step 4.