The part you hold in your hand every day
The steam and water knob gets touched more often than anything else on the machine apart from the portafilter. It is turned, held, turned back – twice for every cappuccino. On top of that comes heat from the inside and milk splashes from the outside. That it eventually shows signs of wear is not a question of quality, but of numbers.
This knob is the version for the Appartamento TCA and the Bicocca, part number A839907912. The cap that fits on top is not included – you can reuse the one from your old knob or order it separately.
When it is time to replace it
The knob needs replacing when the seat inside is worn out and it turns on the valve spindle without anything happening. When it shows cracks that spread under strain. When the surface is so worn that it feels unpleasant to turn. Or simply when it has been dropped and broken – the most common case.
At a glance
| Type |
Knob, control part |
| Location |
on the outside of the machine, on the spindle of the steam and water valve |
| Fits |
Rocket Appartamento TCA and Bicocca |
| Scope of delivery |
one knob, without cap |
| Part number |
A839907912 |
| Version |
without cap – caps with and without logo are available separately |
| Brand |
Rocket |
Who it is for
For anyone whose knob is broken or worn out, and for those who want to treat their machine to a clean control part again after a few years. Rocket used a different knob shape on older series – if you are not sure whether your machine belongs to the TCA generation, send us the serial number and we will check.
What goes with it
You will find the matching caps with and without logo, gaskets and valve parts under Rocket Appartamento spare parts and under Rocket Bicocca spare parts. Further control parts are listed under Rocket accessories and spare parts, the complete range under Original spare parts and replacement parts.
Our routine from Bern and Zurich – not a manufacturer requirement, but what we tell our customers: if the knob becomes stiff, it is almost never the knob itself but the valve behind it. Putting a new knob on a sticking valve only improves things briefly and wears out the new knob just like the old one. So first check whether the spindle turns easily without the knob. Then the obligatory test cappuccino – Nutty Delight is our standard for this, Cozy Chocolate the sweeter option and Very Nutty the bold counterpart. More under coffee beans.
No returns
Original spare parts are excluded from exchange and return. They are sourced specifically for each order and cannot be resold after installation or trial fitting on the machine. So before ordering, please check the model, year of manufacture and serial number of your machine – or drop us a line and we will clarify the fit together. Your rights in the case of defective goods remain unaffected.
Frequently asked questions
Is the cap included?
No. Only the knob is supplied. Caps with and without logo are available separately – let us know which version you need.
Does the knob fit my older Appartamento?
This version is for the TCA generation and the Bicocca. There is a different knob for the older series. Send us the serial number and we will identify the right one.
Can I replace the knob myself?
It sits on the outside of the valve spindle. Only work on the machine once it has cooled down and is depressurised, and do not use force – if something sticks, the cause lies in the valve behind it.
How long does delivery take?
Delivery across Switzerland and to Liechtenstein in 2-4 working days.
Can I see the part in your Showroom?
Yes. We are in Bern at Gerberngasse 44 and in Zurich at Hagenholzstrasse 50b. Bring your old knob along and we will compare them directly.
Questions about the fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
