Rocket HX losing steam pressure

Beginner and pro baristas share tips and tricks.
User avatar

Postby Hooah » Oct 23, 2016, 9:57 am

Hi everyone!

I'm fairly new to Espresso (only at it a year) but I've been reading all of your amazing stories, suggestions, tips and recommendations since I registered. I've searched for answers to my issue and have tried to fix the problem in several steps but it's a persistent bastard.

Rocket Cellini Evo V2, bought used over 6 months ago here in Germany. It's been working fine until a few weeks ago, when pulling a double shot while steaming the pressure drops to .5
Nothing has changed over the last 6 months. Same water, same electrical plugs, same warm up time, same everything.
So I bumped up the pressure from the stock 1.1 to 1.3bar and though I saw a slight improvement in steaming but the cooling flush was 3 times longer than before. And yes I purge the steam wand and wait for the heating element to kick in and start raising before I pull the shot and start steaming.

So I pulled the mushroom and it looked brand new.
Pulled the water level probe and it was pretty clean but I used a green pad anyways.
Pulled the safety valve today and looked inside the boiler for scale, barely any but I used some citric acid to take care of that.
Flushed several times, warmed up for 45 min and made my typical 2 cappuccini. Still dropped to .5 towards the end of steaming.

Espresso and cappuccino taste good so no HX heating problems, and it has the original 2 hole steam tip installed. I'm just at a dead end and hope someone can give me a tip of what to check next. I want to fix it before I sell her in the next few months get a lever :)
Thanks for any help!


Postby h3yn0w » Oct 23, 2016, 10:14 am

Boiler fill probe faulty or scaled? Just guessing as maybe the water level in the boiler is not where it should be. Is the boiler filling while you are steaming?

I try to steam when the pressure is rising and near the top of the cycle. These machines are steam monsters.

User avatar

Postby Hooah » Oct 23, 2016, 10:18 am

Yes it's filling while I'm pulling a shot, I checked. I pulled the probe and it looked clean but I touched it up with green pad anyway. I also wait until the heating element is about to cycle off before I start my pull and steam but it doesn't help.


Postby DrJ » Oct 24, 2016, 12:14 am

Although not an answer, Rocket recommends that you do not de scale the machine....

User avatar

Postby Hooah » Oct 24, 2016, 12:18 am

I didn't plan to but since I wasn't sure what the previous owner used for water I wanted to eliminate scale as a reason for my problem. I only descaled the boiler, with a very weak mix of citric acid, then siphoned it all out so it didn't go through the entire machine. There was so little scale that it only took 10 minutes to dissolve.


Postby davebm » Oct 31, 2016, 8:58 am

I own a Rocket Evo 2 too (wow thats confusing). My pressure was set to 1 bar stock and I pushed it up to 1.1 to help with recovery time between shots. In terms of steaming - the pressure starts to gradually drop as you start steaming and generally settles at around 0.5 bar. I am not sure if that is a problem as it occurs on my machine, I thought it just made sense because technically you are releasing pressure? I think I may have misunderstood your problem :(

User avatar
Team HB

Postby homeburrero » Oct 31, 2016, 1:39 pm

davebm wrote: In terms of steaming - the pressure starts to gradually drop as you start steaming and generally settles at around 0.5 bar. I am not sure if that is a problem as it occurs on my machine, I thought it just made sense because technically you are releasing pressure?

Makes total sense. When the wand is open on these machines you hit an equilibrium where the heater is on and producing steam at the rate that it is escaping. The pressure will slowly drop to a point where the steam is releasing at the same rate that your element can produce it. On my Evo V2, with the stock tip, my equilibrium point is just over 0.6 bar. (And if I start at 1 bar it takes a full minute to drop that far.) A higher wattage element will support a higher equilibrium pressure, as will a tip with fewer or smaller holes. A higher pStat setting will not change that equilibrium point, but of course will give you a little more time before it drops to that point.

If an autofill kicks in while you are steaming, then the introduction of cooler water into the boiler causes the pressure to quickly drop, even below 0.5 bar because of the sudden steam condensation in the boiler caused by the lower temperature.

In an earlier post, the OP said:
Hooah wrote:Yes it's filling while I'm pulling a shot, I checked.

If so, that would certainly cause a significant drop in the boiler pressure when the autofill kicks in. One thing you can do to avoid that is to force an autofill right before pulling a shot. Open the hot water wand for half a second, then close it and wait a second or two. Repeat until you hear the boiler fill, then start your shot pulling and steaming with the boiler near its maximally full point.
nínádiishʼnahgo gohwééh náshdlį́į́h

User avatar

Postby curmudgeon » Nov 02, 2016, 9:31 am

This may be a bit of a sidebar, but how do you know the boiler is filling when you're pulling a shot? If that's the case, you couldn't pull a shot at full pressure as that was happening, since you're dividing pump output between boiler fill and HX use, right? How can you tell it's filling? Does the pump noise change?

Now, if the boiler was filling when steaming, I get that that's a much more identifiable scenario.

:?: :?:

User avatar

Postby Hooah » Nov 02, 2016, 9:38 am

The water level in the tank drops slowly as does the boiler pressure during a shot.

I had first noticed the problem during a very long pull (40 seconds with new beans :roll: ) while steaming. The boiler pressure dropped below .5 bar and ran out of too much pressure to continue to steam. Since then I've been pulling 23 second shots while steaming and pressure still drops to .5 - .6 bar

User avatar
Team HB

Postby homeburrero » Nov 02, 2016, 10:50 am

It is a little hard to tell whether or not a boiler fill is actually happening while trying to pull a shot. The pump is pulling from the reservoir irrespective, so the drop in reservoir level is not a reliable indication. You also may not see anything at the brew pressure gauge. You would, however, see a precipitous drop on the boiler pressure gauge.

If you have a good check valve and a bad autofill solenoid, it seems possible that you might have water filling the boiler every time you pull a shot. One way to check this would be to first trigger the normal autofill using the water wand, then run a series of long backflushes with a blank filter (and doing no steaming.) If your solenoid is leaking you will see a drop in boiler pressure, and may see water spurting out of the anti-vac valve if the boiler overfills to the top.
nínádiishʼnahgo gohwééh náshdlį́į́h