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Rotary pumps are the class act of prosumer level espresso machines. They are quiet, robust, and in most cases, if a machine has a rotary pump it is plumbable directly to a water line. However, some users advocate for vibration pumps. They say they build up brew pressure more slowly, resulting in a sort of pre-infusion that makes a better espresso.
Today, I’ll put that to the test and pull shots side by side on nearly identical machines, except one has a rotary pump and the other a vibration pump. I’ll control the variables as much as possible and see if we can find any difference in espresso quality based on pump type.
So this question actually came up during our live review of the full-line of Rocket espresso machines last week, and we covered it there, but I wanted to take a closer side by side look. If you missed our full-line review you can use this link to check it out.
For our test, I’ll be using a Rocket Mozzafiato Evoluzione R equipped with a rotary pump and a Rocket Giotto Type V with a vibration pump. Both are heat-exchange boiler PID machines, and with the exception of the pumps are pretty much identical internally.
I chose the Rocket machines for this because, well, I had a bunch of them out from our review, but more importantly, Rocket is one of the few companies that makes a set of machines that are nearly identical with the exception of pump type. It's also nice that they are PID, so getting accurate matching brew temps for the test was easy.
For other variables, I’ll be using Lavazza Top Class Coffee, and my grinder is the Rocket Macinatore FAUSTO. Grind size is the same for both shots as well as dose at 17.3 grams each. I ground and weighed in a cup for accuracy and was careful to distribute the grounds evenly in the portafilters. I used an Espro calibrated tamper with a convex base to assure a consistent pressure on both tamps.
It takes longer for the first drip on the vibration pump machine as the pressure builds up so it turns on first. The rotary pump machine reaches more than 8 bar of pressure almost immediately, while the vibration pump is at about 2 bar even after being on for 2 seconds longer.
At first drip, the vibration pump has been running for about 7 seconds and is at about 5 bar of pressure. As the shots progress, they pour at the same speed. The pressure on the rotary gauge is steady, but it bounces between 8 and 9 bar on the vibration pump machine.
There is some pressure variation, and it seems to coincide with the PID briefly energizing the heating element in the vibration pump machine. The rotary pump delivers a consistent pressure even when the PID was briefly energizing the boiler.
As the shots continue, they begin to look quite different. The crema in the rotary shot is darker, more consistent in color, has finer bubble structure, and runs deeper into the glass. Overall, a much nicer looking shot.
Both shots finish at a volume of 60 milliliters and 29 seconds after first drip. As the shots settle out, the crema layer is much deeper and more uniform on the rotary shot, while the vibration pump shot's crema quickly fades and has a very distinct color difference and a coarser bubble structure.
Tasting the shots, there was quite a difference. The shot from the rotary pump had richer, deeper flavor and a more favorable mouthfeel, while the vibration pump shot was thinner and not nearly as bold. Using the same coffee, grind size, dose, and brew temperature, the rotary pump clearly produced a better shot.
Based on shot quality in this test, I prefer the rotary pump machine. Plus there’s the ease of use. On a plumbed-in machine with a rotary pump you never have to fill a reservoir. Going from a reservoir machine to one that’s plumbed in? For me, that ease of use and never worrying about running out of water is a life changing experience.
If you’d like to learn more about Rocket Espresso’s PID’d Mozzafiato and Giotto machines, use the link here to see my video which covers both with either the rotary or vibration pumps.