Waterstop may be a backflow valve. Most cities require them to prevent water from backwashing into the city water supply." -cannonfodder

Just FYI as info: In my system, which had a slight cavitation problem with the same machine, my plumber installed "check valves", which sound like the same thing as a "backflow valve." From the main cold water supply, I have a fork to a 3M/Cuno Espresso Filter (ESP 124-T) which goes to a filter water tap and (another fork) to the espresso machine. There are check valves between both the 3M filter and the espresso machine. When I use the filtered water tap, I get plenty of water (too fast, I don't open it up much when using it). Between the espresso machine and its' check valve, there is also a small quarter-turn shut off valve. The small 'accumulator' I installed is between that quarter-turn shut off valve and the espresso machine. It cured my cavitation problem. A factor I had not thought of before, but I'm thinking of it now, is the length of tubing between the water filter and the machine - there is the braided tubing that goes from the machine to the shut-off valve, and then there is the check valve, and then more tubing to the espresso filter (another 6 ft or more). The only difference between the water to the filtered-water tap and the espresso machine is the length of tubing to its' destination.

Because there does not appear to be any water flow problem to the filter water tap (a very short distance) I am wondering if the sheer length of the feed line (can't measure it now, but it must be ten or twelve feet) to the espresso machine is a factor?

Hello everyone

Thank you very much for your replies. Sorry it has been a couple of days - somehow I havent received notifications of your posts. Anyway today i made some more "amateur experimenting" to clarify the problems:

I tried to take off the hose at the machine. I checked how much water the plumbing delivers. A 1 liter bottle is filled in maybe 10-15 seconds. I therefore think the problem is not "starving" for water as suggested. Do you agree?

My next experiment was made before putting the hose back on. I tried to slowly open the water to make the hose deliver water much more slowly, (filling a glass of water in maybe 10-15 seconds). I put the hose back on the machine with this setting of the water. (I have another place to cut off the water that made this possible).
The problem was the same though.

My third experiment: I turned the water back to full speed. Now i tapped a lot of the machines boiler water from the tap forcing the machine to autofill for quite some time. (so it made the annoying noise). While it was doing this i tried to very slowly and gradually to minimize the water supply (to deliberately starve the pump) but only till i cold hear the pump react to the lack of water. The sound was there all along.
(I know this sounds rather dramatic but i honestly only turned the the water off very slowly and turned it back the moment i could hear the reaction from the pump)

So now Im quite confused: I dont think a accumulator would help me and I dont thing a restriction valve would either?

I added a couple of photos as suggested by Eric.

Any other suggestions. Malfunction of the pump? Just strange when there is no problem when its not plumbed in?

Best regards Soeren

erics wrote:An important point to say the least.

How about some pics of your water path installation? What does your brew pressure gage read after you have pulled a shot?

When the machine is not in use - the brew pressure gage reads 3 bar. After plumbing it in I regulated the screw for the pump is decribed int the manual to 9 bar with the blindfilter in the portafilter.

One last quiz

With the machine OFF, lift the brew lever with no portafilter in place - now what does the gage read?

Well, maybe not



For the items encircled in red, the brass item is the pump pressure adjustment but what is everything else? The machine came with a supply hose - is that the only thing you have connected to the machine in the red circle?

Hello Eric

In the red circle I connected the water supply.

What you also see is a small bracket i mounted together with one of the nuts under the machine. Its to keep the hose from the drip tray in level to make it drop all the way. Its well tightened and im sure this is not causing problems.

Ill take some more/better pictures of the connections if it would be helpful.



Last night i explained my problems to Rocket Espresso - the manufacturer and they have kindly responded already this morning with an interesting explanation:

Thank you for your email and support of the Rocket Espresso brand.

I think that your machine may need a small adjustment to the one way valve that is after the inlet water solenoid.
The noise is not a fault but the spring and non return valve ball need some additional tension to stop them oscillating as the water from the line fills the machine.

The work required to do this is not difficult so long as you are reasonably competent with mechanical things!

The process requires you to open the machine, remove and adjust the valve and then re assemble the machine.
If you feel that you are comfortable doing such work I can send you the details of what is required to fix this problem.

What do you think of this explanation Eric - does it sound likely?

The brewhead pressure in off-position i will check when I get home from work.
(...which reminds me that maybe i should START working instead of sitting at my desk posting at Home Barista )

What do you think of this explanation Eric - does it sound likely?

Yes, I'm aware that the Rocket machines with a rotary pump have a solenoid(s?) that allow for switching between the reservoir and a pressurized supply for water but am not familiar with exactly how they do this.

Evidently the check valve is designed around a particular inlet pressure range and that range is a little too narrow for some installations. The content of their response seems as though they have seen this problem before and the solution is a tested and proven one. So yes, I would "go for it". See if you can obtain their permission to repost their instructions in their entirety - I would be happy to help you with that.

Hello Eric

I sure will ask if I can post the explanation. If successful ill also post a picture of the valve ball that is "singing in my kitchen".

Now I cant wait to get home to take the machine apart - I better wait for the instruction from Rocket though AND I better do it when my wife is not home!
(Like the day i drilled holes in our new kitchen and took the plumbing apart )

Noise: Pump or valve ball? On my machine the pump is on the right side of the machine (facing it) toward the front third, and the solenoid that routes water from either tank or line is far away from that, on the back of the other side of the machine. So the noise (buzz) location would perhaps tell you something. Of course, I realize my machine may be configured differently than yours, or use different components - mine is a fairly early model. Will check mine out whenever I get back home - I'm getting curiouser.

Hi Al

Thx for you contribution. Im at work right now, but as far as I can remember, the noise is coming form the back of the machine - im quite sure of that.
Rocket wrote me again yesterday evening and said that he'd expected to mail me with the detailed instruction of exactly what to do inside the machine.

Ill keep you informed as soon as theres any news

Best regards Soeren