Take a look under the hood of coffee machines and find out what the quality ones have there. It's a reliable ULKA pump and a well-adjusted OPV valve. Do you know why they are there and how they work? Here are the answers.
Why is the ULKA pump used in coffee machines?
The coffee machine needs a pump. Otherwise the required pressure would not be 6-9 bars for espresso preparation did not arise. Unless it is a professional or one of the more expensive home (semi-professional) coffee makers, the pressure generator in the coffee maker will not be a rotary pump, but a vibrating pump.
There is a fairly wide selection of vibration pumps on the market and they vary in both manufacturer and quality. An important factor for evaluating the quality of a vibration pump for a coffee machine is especially durability, noise and pressure stability . Industry leader and The king of vibration pumps is ULKA . These are Italian pumps with a long service life, usually 15-30,000 cups and 4-8 years .
ULKA engineers love innovation, which is why their models are constantly being improved. For example, the world's most widely used pump, the ULKA EX5, has replaced its original plastic outlet with a brass one and can pump 300 cc at 9 bars . The maximum pump pressure climbs to 15 bars without spoiling the good impression of coffee preparation with significant noise.
The given "flow rate" means that the pump can push out about 300 ml of water/min , while for espresso you typically need 30-60 ml/30s. Therefore, it is absolutely sufficient for the stability of home coffee preparation and at the same time it has a decent reserve until exhaustion.
Why is it good to have an OPV valve in an ULKA coffee machine?
Pump power is one thing, but coffee needs are another. And a perfect espresso needs a pressure of between 6-9 bars during preparation. However, the robust ULKA unstoppably sends up to 15 bars. What about that? The solution is the OPV (Over Pressure Valve). The ensures the optimal number of bars during espresso preparation. It keeps the pump performance in check and also ensures its service life by transfers excess pressure back to the boiler .
Well set OPV is the key to great espresso extraction and the long-term health of the coffee machine. But not all coffee machines have it. With cheap coffee machines without this technology, you risk making coffee with a completely bad taste. Without OPV, the following problems can easily occur:
- over-extraction : high pressure leads to rapid extraction and instead of a full-flavored espresso, you have an astringent, bitter "something" in your cup
- channeling : the unfiltered force of the water will penetrate the coffee in a channel-like manner, resulting in an unbalanced coffee combining unpleasant bitterness and acidity at the same time
Which coffee machines have both OPV and ULKA pumps?
If you take one thing away from this article, it's this: "if a coffee machine with a vibration pump, then ideally ULKA with integrated OPV" . So which coffee machines have this in common? Among the popular home coffee machines, these are especially Rancilio Silvia , Anna Lelit or maybe Rocket Espresso .
Which coffee machines do not have both an OPV and ULKA pump?
AT cheap lever coffee makers under 3000 CZK are often cheaper vibration pumps without OPV. The same is true for many capsule coffee machines. And of course there is also the segment travel coffee makers and domestic with pressure generation by its own power , such as Flair manual coffee maker or a range of manual coffee makers from La Pavoni .
Conclusion and FAQ
Many users of home coffee makers with these technologies have already realized that the combination of the ULKA pump and the OPV valve is not a coincidence, but a proven recipe. The ULKA will deliver reliable performance - or rather pressure, and the OPV will ensure its optimal use.
How is ULKA different from other vibration pumps?
Compared to cheaper alternatives, they have better quality construction and materials (for example, brass terminals instead of plastic). The key is that they provide more consistent pressure , which is what you need for good espresso.
How do I know if my coffee machine's OPV valve needs adjustment?
If you have a coffee maker with a pressure gauge, watch it during extraction and it should show about 9 bars . With other coffee machines, you can recognize a problem with high pressure by the taste, when such an espresso is too bitter and astringent.