Sour espresso with Rocket Appartmento

Need help with equipment usage or want to share your latest discovery?

#1: Post by Antyk »

Hey, I recently bought a Rocket Appartmento machine.
I've done 20-25 shots so far. Unfortunately they are all sour.
I started with stock double dose basket and 18 grams of coffee. I try to stick to the rule of 25-30 seconds and ratio of 1:2.

My first couple shots were under 20 seconds, but I was able to find a grind setting, that let me yield 36 grams of liquid. Unfortunately it was very sour, that is was hard to cover even with milk. I tried three different coffees. Two are medium roast and the last one is dark. The result is pretty much the same.

The best result I had with 18 grams of coffee, ~40 seconds of time and 55 gram of liquid. Still it was sour and a little bit burnt at the same time.

I did a couple random tests to check if the result will vary.
For example:
1. 18 grams of coffee and finer grind - 60 seconds to yield 36 grams of liquid, burnt taste
2. 18 grams of coffee and coarser grind - 30 seconds to yield 55 grams of liquid, very sour
3. 14 and 16 grams with finer grind - in range of 25-30 seconds, but still very sour.

I read that there might be a problem with temperature. I started to brew after 20 mins, 30min and 70 minutes from machine start. Also, I flushed different amount of water each time. The result is pretty much the same.
Unfortunately, I don't have a pressure gauge nor thermo gauge.

Moreover, in case of brewing 10 shots in a row I can see that in the same settings the brew time can decrease.

By the way, I use stepped 1ZSPRESSO hand grinder and I use 14-18 steps from the most finest setting.

Could please point me a direction where should I move? Thanks in advance :)

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#2: Post by espressotime »

Perception. Call it fruity and convince yourself you are tasting notes of berries and apple.

Supporter ❤

#3: Post by Milligan »

Are you new to home espresso or just to the machine? Sounds like it may be a case of bitter/sour confusion. If a 20s shot tastes sour to you and a 50s shot tastes sour then I'm thinking you need to dial in your taste buds a bit. Good espresso is a hard target to hit so it isn't unexpected that you will be 20 shots in and nothing tasting great when starting off. Some coffees are a roll of the dice on the first few shots even if you dialed it in perfectly the day before. Switching from light to medium to dark makes it even harder. Typically my light settings are lightyears away from my dark settings and much harder to hit well.

My advice is stick to one known good coffee and practice a lot on it. Buy 2lbs. Stick to one dose, time target, and temp. Adjust grind only until you get something drinkable. Bring other family members or friends into the tasting to get feedback. Some folks are much better at picking out sour and bitter so that helped me when I first started. Personally, I'd probably suggest picking up some Illy Classico or similar to begin on. They typically have a wide range where you can get a decent shot of it, is ubiquitously available for the most part, and show bitter/sour quite well at both thresholds.

Good luck!


#4: Post by dockoelboto »

You should consider a temp probe. The hx appartamento can run very hot and may need to check your pressure stat. Plus your may have to flush a ton to get the temp down. A must addition to the machine. IMHO

Team HB

#5: Post by JRising »

I'm hesitant to offer any suggestions when I can't actually see, feel and hear the machine while it's brewing, anything I assume is more likely to be misleading than it is to be helpful.

Does your pressure gauge seem to work well enough to trust? Ie. does it show zero when you know the boiler is cold and at atmospheric pressure, then start to rise steadily after you hear the vacuum breaker go "shhhhhlup"? What does your pressure gauge show while the machine is idle probably something like 0.9, rising to 1.2 with element, then slowly dropping back to 0.9 with element off?

How long into your cooling flush do you hear/see the steam stop and the liquid take over the showerface filter?

My gut reaction to "Sour" is that the brew-water is probably not hot enough.


#6: Post by Bluenoser »

I agree with the poster about the temp probe.. I also have had an HX for a while and had sour shots at the beginning.. It's also easy to confuse sour/bitter at times.. But you can't nail down the issue until you know what your brew water is doing and you can't hope to do that without a group head thermometer. Bite the bullet and install one and you'll be glad you did down the road.. Look up the flush-wait vs flush-go varieties.. I often flush-wait and you'll find your brew water is likely about 2-3F below what your group thermometer will read at about 15 seconds into the shot. The group thermometer can also help to tell you after you flush, when to pull your shot.. Using HX designs are a real education.. more than you likely bargained for going in.. and there are few retailers that really tell you how to get the best out of your HX. Once you get learn to characterize your machine you'll be fine and it will make good shots.. But there are no monitoring points in home HX machines and you are just guessing at your brew water temp.. Lots of threads on HXes and the Appartmento here.. One guy even hooked up a fan to his E61 group and install another probe to control it.. The E61 will take about 30 minutes to warm up.. The rocket has a 3mm restrictor, I think, and its rebound should be pretty quick..

My sour shots were because my group was not getting back up to temp between shots and my brew water was successively getting cooler.. Shot 1 was okay.. Shot 2 worse.. Shot 3 really sour. The group thermometer will tell you that.

I'm not thinking that is your exact issue.. but you need to first get consistent brew water temp and that requires a group thermometer (IMO) and it is also nice to borrow a SCACE at some point down the road to see how the group thermometer tracks the brew water temp that exits the screen.. there willl be some difference..

Once you can control the brew water temp.. you can develop a consistent flush routine. Read the back threads on HX problems here.. lots of good info.

Antyk (original poster)

#7: Post by Antyk (original poster) »

Thanks a lot for the feedback.
Today I flushed about 200ml of water before a shot. This time it was more drinkable. Still too far away from what I would call a nice shot.

The pressure gauge shows 1 bar before the brew. Overall I did 3 shots today so far. For the first one it was 1.2 bar as soon as I put the lever up. When the water started to flow it dropped to 1 bar. The following 2 shots had 1.2 bar at the beginning and 1.1 after the water started to flow.

I was able to find a pressure gauge for the group head. It will arrive in 2 days. Unfortunately, I was unable to find a group thermometer on the local market. There are available options in Europe, but they aren't able to send one because of the ongoing war in my country. I guess a thermometer in a coffee cup won't be that helpful.


#8: Post by larscoffee »

I also have a Rocket Appartamento and have had issues. It has helped weighing and timing shots, using a WDT device, and a spring-loaded tamper.

Beyond your puck prep and workflow, I've uncovered that my machine was set to 12bar pressure by default. You can lower the default pressure by untightening a valve that is located beneath the water reservoir. Hard to change without a pressure gauge, but it was about 2 full turns. I picked one up for $30 online. Taking the housing of the machine off is like 10 screws, alan keys and Philips, and the whole mod took me about 30 minutes. Whole Latte Love had a few videos about it that helped me do it.

There are lots of forum posts about finding the ideal brew temperature for the rocket. I recently purchased a temp gauge for the grouphead to better monitor the temp on output. It sounds like with your flushing, you are off to a good start.