The lock nut on the drain elbow – the part that keeps the drain path sealed
On Rocket’s commercial machines, waste water runs from the drip tray through an elbow down into the drain box and from there into the hose. This elbow is pushed through the tray’s sheet metal and tightened from below with a lock nut. It is the nut that keeps the connection dry.
Because coffee residue, milk splashes and rinse water constantly run through it, this is the dirtiest spot on the whole machine – and accordingly the one where a nut is most likely to corrode in place, wear out or get lost during cleaning.
When it needs replacing
The lock nut should be replaced if water leaks out under the drip tray instead of running into the hose; if the drain elbow can be turned by hand because the nut no longer grips; if the thread is worn or scaled and no longer turns cleanly; or if it disappeared down the sink during the last cleaning.
At a glance
| Type |
Lock nut |
| Location |
under the drip tray, on the drain elbow |
| Fits |
Rocket Boxer, RE A and R9 |
| Scope of delivery |
one lock nut. Drain elbow and sealing ring are not included |
| Part number |
M619905574 |
| Version |
Original Rocket part |
| Brand |
Rocket |
| Installation |
Installation by a qualified technician recommended |
Who it is for
For bars and workshops that run a Boxer, RE A or R9 continuously and take the drain path apart during servicing anyway. The part costs little and belongs in every service drawer – precisely because it is often missing when reassembling.
Important for installation
The nut sits in the drain path and is tightened from below against the sheet metal. Start it by hand and tighten it only as far as needed for the connection to be sealed – too much force distorts the tray’s sheet metal or strips the thread on the elbow. The sealing ring should always be renewed; it is not included here and is listed as a separate item in the catalogue: O-ring for the drain elbow. We also stock the elbow fitting itself separately, in case its thread has been damaged. Before starting work, switch the machine off, disconnect it from the mains and let it cool down.
What goes with it
The three parts of this feed-through belong together: the elbow fitting for the water drain with number M439905384, the O-ring for the drain elbow with M449905463 and this lock nut with M619905574. Once you open the drain, it is best to replace all three at the same time. The other parts for this machine are listed under Rocket Boxer spare parts. If the machine is in for maintenance anyway, you will also find the Boxer brew group there. For the full overview, see Rocket accessories and spare parts.
Workshop tip from Bern and Zurich
When dismantling, we never put the lock nut down on the work surface, but straight into a small bowl together with the sealing ring. Sounds pedantic, but it regularly saves half an hour of searching the workshop floor.
And because no repair ends without a tasting for us: afterwards an espresso with Nutty Delight, Cozy Chocolate or Very Nutty runs through the group. The full selection is in our coffee beans. 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 sourced specifically for each order and cannot be resold after being installed or test-fitted on a machine. So before ordering, please check the model, year of manufacture and serial number of your machine – 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 the sealing ring included?
No. The item only includes the lock nut. We have recently started stocking the matching O-ring for the drain elbow as a separate item – best to order it at the same time.
Is the drain elbow itself included?
No, the elbow is a separate part. Here you only get the nut that tightens it. The elbow fitting M439905384 is listed as a separate item in the catalogue.
Does the nut also fit an R9 One?
The documentation lists Boxer, RE A and R9. We cannot tell from it whether the R9 One has the same drain, so we do not claim it does. Send us the serial number and we will check.
What wrench size does the nut have?
We do not have a dimension for it. We only state what is in the documentation, and here that is the part number and the machines.
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 fits 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.
