The 36 mm Teflon ring of the brew group
At 36 millimetres, this ring is the largest of the five Teflon seals in the Rocket catalogue – and the only one you recognise immediately when dismantling. It seals the brew group at a large-area joint, in other words where two bodies meet and a flat gasket is needed instead of a cord seal.
Unlike rubber, Teflon stays dimensionally stable even after years in hot water and does not become brittle. On the other hand, it has no spring-back: once it has been flattened, it stays flat. That is why the ring is one of the parts you always order along with everything else when opening the group, rather than hoping the old one will hold one more time. The part number is C469900421.
When it is due
Water is standing at the parting joint of the group, where it has no business being. After heating up, there is a brief hiss at a spot that used to be quiet. The brewing pressure drops faster than usual because part of the pressure escapes sideways. And whenever the group is open anyway – the ring costs less than a second round of work.
At a glance
| Type |
Teflon O-ring |
| Location |
Brew group |
| Fits |
Rocket machines with this brew group – the documentation does not list any models |
| Scope of delivery |
one O-ring |
| Part number |
C469900421 |
| Design |
Teflon (PTFE), 36 mm; the documentation does not say whether the dimension refers to the inner or outer diameter |
| Installation |
Installation by a specialist recommended |
| Brand |
Rocket |
Important for installation
The ring sits in the water path of the group, which is under pressure. Machine unplugged, depressurised, cooled down – in that order. Teflon needs a clean seating surface: limescale residue on the sealing surface is not compensated for by the ring; instead, it presses into the ring at certain points and creates exactly the leak you wanted to fix. We do not give step-by-step instructions here because the group is pressurised.
Who it is for
For workshops and for anyone dismantling the group of their Rocket as part of an overhaul. If you are unsure whether your ring is this one or one of the smaller Teflon seals, measure the old one and send us the dimension – that is quicker than guessing.
What goes with it
In the same job: the Teflon seal for the relief valve, the Teflon seal for the mushroom-head screw, the fine filter of the brew group and the camshaft. For an overview, see Accessories and spare parts Rocket and the spare parts.
The Teflon seals in the Rocket catalogue
We stock five Teflon seals individually. They look similar and sit in quite different places – the part number decides, not the shape:
From our workshop in Bern and Zürich
Before the new Teflon ring goes in, we wipe the sealing surface with a soft cloth and a little warm water and look across it in raking light. You only see limescale when the light falls flat. That is our routine, not a manufacturer specification. We then do the test brew with a reliable bean, such as the Nutty Delight, the Cozy Chocolate or the Very Nutty. The full selection is under Coffee beans.
Returns excluded
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
Is this an electrical part?
No. It is purely a Teflon seal, with no electrical function.
Is the 36 mm the inner or the outer diameter?
The documentation does not say. We pass on the figure as the manufacturer states it and make no claims about it. Measure the old ring or send us a photo with a scale.
Does it also fit a Rocket other than mine?
The documentation does not list any models for C469900421. Send us the model and serial number and we will check the fit before you order.
Why Teflon and not rubber?
Teflon withstands temperature and pressure permanently and does not become brittle. On the other hand, it does not spring back – which is why it is replaced on opening and not reused.
Can I look at the part in your showroom?
Yes. We are in Bern at Gerberngasse 44 and in Zürich at Hagenholzstrasse 50b. Let us know shortly beforehand and we will have the part ready.
Questions about the fit? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
