The small washer that keeps the knob snug and free of play
Between the steam and water knob and the housing panel of your Rocket Evoluzione or Premium Plus sits a flat washer. It keeps the knob at a distance from the panel, spreads the force over a larger area when opening and closing, and prevents the knob and the panel from rubbing directly against each other. The part number is A829904375.
You only notice this part when it is missing or worn. Then the knob suddenly has play, sits lower than usual, scrapes audibly against the panel when turned, or a bare ring appears on the surface. Anyone who has taken the steam and water valve apart during a service sometimes finds the washer bent or cannot find it at all – then it should be replaced before the knob is refitted.
When it is due
These signs point to a new washer:
- The knob wobbles sideways or can be pushed back and forth.
- When turning, there is scratching or grinding between the knob and the housing panel.
- The knob sits visibly lower than the one on the other side of the machine.
- A bare friction ring has formed on the panel.
- After a service, the old washer is bent, worn or can no longer be found.
At a glance
| Type |
Washer, flat |
| Location |
Between the steam/water knob and the housing panel |
| Fits |
Rocket Evoluzione and Premium Plus |
| Scope of delivery |
One washer |
| Part number |
A829904375 |
| Design |
Dimensions and material are not specified in the documentation |
| Installation |
Fitting by a professional recommended |
| Brand |
Rocket Espresso |
Who it is for
For anyone who is overhauling the steam or water valve of their Evoluzione or Premium Plus anyway and wants to renew the small parts at the same time. A wobbly knob is not a cosmetic problem: the play is transferred to the shaft and, over time, works its way into the seal. If you replace it together with the shaft and the seals, you will have the valve back under control for many years.
Important for installation
The knob sits directly on the steam and water valve, and behind it is a boiler under pressure. Before any work, the machine must therefore be switched off, disconnected from the mains, completely cooled down and depressurised. We deliberately do not provide step-by-step instructions for this part – the work belongs in experienced hands. If you are unsure whether the washer fits your serial number, send us the number and we will check the fit.
What goes with it
From our workshop in Bern and Zürich
When we open a steam valve, we lay out the small parts on a light-coloured cloth in the order they were removed – washer, plate, clip, shaft. That way nothing gets lost during reassembly and nothing ends up the wrong way round. This is our routine, not a manufacturer's specification. Afterwards we pull an espresso as a check, usually with Nutty Delight or Cozy Chocolate; if you like it stronger, take Very Nutty. The full selection is under Coffee beans.
Returns excluded
Original spare parts are excluded from exchange and return. They are procured specifically for each order and cannot be resold after installation or a trial fitting on the machine. Therefore, check the model, year of manufacture and serial number of your machine before ordering – or drop us a quick message and we will clarify the fit together. Your rights in the event of defective goods remain unaffected.
Frequently asked questions
What are the dimensions of the washer?
The documentation for A829904375 does not say, and we do not make up a number. If you still have the old washer, measure the inner and outer diameter and send us the values – then we will compare before you order.
Is this an electrical part?
No. The washer is a purely mechanical small part without any electrical function. However, it sits on an assembly with pressure and heat behind it – hence the note on installation.
Do I need one or two washers?
One washer is supplied. Machines with separate steam and water valves have two knobs; if you overhaul both sides, order it twice accordingly.
Does it also fit the Appartamento or the R58?
These model series use different knobs and different small parts. According to the documentation, the number A829904375 is assigned to the Evoluzione and the Premium Plus. For other models, send us the serial number and we will find the right part.
Can I see the part in your showroom?
Yes, of course. You will find us in Bern at Gerberngasse 44 and in Zürich at Hagenholzstrasse 50b. Bring your serial number or the old part along, and we will compare right there on site.
Questions about the fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
