The lock nut for the sealing plug – so the drip tray stays watertight
At the bottom of the Rocket drip tray there is a sealing plug. If you run the machine from the tank, you leave it in and empty the tray by hand; if you connect it to the mains water supply, you take it out and route the drain downwards. This plug is held by a small lock nut with a 1/8 inch thread, and that is exactly the part meant here – together with the O-ring that seals the connection.
The part is inconspicuous and inexpensive, but if it is missing or the O-ring has hardened, water runs out underneath the machine instead of staying in the tray. Usually you only notice when the kitchen counter is wet.
When it needs replacing
The lock nut needs replacing if water leaks from the underside of the drip tray even though the plug is tight; if the nut can no longer be tightened because the thread is worn; if the O-ring is hard, brittle or torn; or if the nut got lost while cleaning the tray – which happens more often than you might think.
A damp ring on the counter under the machine is the classic first sign. Before you look any further, turn the tray over and check the screw connection on the bottom.
At a glance
| Type |
Lock nut with O-ring |
| Thread |
1/8 inch |
| Installation location |
Bottom of the drip tray, on the sealing plug |
| Fits |
Rocket machines with a closable drip tray drain. The documentation does not state which model series these are |
| Scope of delivery |
one lock nut with O-ring. The sealing plug itself is not included |
| Part number |
A329904369 |
| Version |
Original Rocket part |
| Brand |
Rocket |
| Installation |
Installation by a specialist recommended |
Who it is for
For anyone switching their Rocket from tank operation to mains water or vice versa and noticing that the small part is missing. And for anyone tracking down a leak under the drip tray.
Important for installation
The nut sits in the water path. It is started by hand and then tightened only until the O-ring visibly sits snugly – with force you strip the fine 1/8 inch thread out of the tray bottom, and then the whole tray is ruined. Before starting work, switch the machine off, unplug it and remove the tray completely. We deliberately do not give step-by-step instructions here: the procedure depends on the model series, and if in doubt, the work belongs in a specialist workshop.
What goes with it
We stock the matching sealing plug with O-ring as a separate item. If you have the tray in your hands anyway, you will also find the plastic collection container in our shop. Everything else is in Rocket accessories and spare parts and in the Original spare parts section.
Workshop tip from Bern and Zurich
With every machine that comes in for service, we turn the drip tray over once and look at the screw connection on the bottom. Two out of three supposedly leaking machines are not dripping from the boiler, but simply from a loose lock nut.
And because no repair ends without a tasting at our place: afterwards an espresso with Nutty Delight, Cozy Chocolate or Very Nutty runs through the group. You will find the full selection in our Coffee beans collection. This is our own routine in the workshop, not a manufacturer requirement.
No returns
Original spare parts are excluded from exchange and return. They are procured specifically for each order and cannot be resold after installation or a test fitting on the machine. So 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 case of defective goods remain unaffected.
Frequently asked questions
Is the O-ring included?
Yes, the documentation explicitly lists this item with O-ring.
Is the sealing plug included too?
No. We stock the plug as a separate item, also with O-ring.
Which Rocket models does the nut fit?
The documentation gives no model list for this number, so we do not state one. It belongs to the closable drip tray drain. Send us the model and serial number and we will check the fit.
What are the dimensions of the nut?
The documented thread is 1/8 inch. Spanner size, height and material are not stated in the documentation, so we do not give them.
Can I see the part in a showroom?
Yes. Bring the removed part to our Showroom in Bern at Gerberngasse 44 or in Zurich at Hagenholzstrasse 50b, we will compare it directly with the spare part and you can take it with you right away.
Not sure whether the part belongs to your machine? Send us the model and serial number at [email protected] and we will check the fit for you. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
