Small, inexpensive and still the reason it drips
An O-ring with an inner diameter of just under eleven millimetres disappears between two fingertips. And yet it is the most common cause of a damp spot inside the machine. It seals by deforming in its groove – and over the years it takes on exactly this deformation as a permanent state. It is then still in place, but it no longer presses.
EPDM with a hardness of 70 ShA is the standard for hot water. The material stays elastic at high temperatures and also tolerates descaling cycles. Even so, the rule is: an O-ring that has been removed is not refitted, even if it looks intact. It costs less than doing the job a second time.
When it is due
Moisture or a white limescale ring appears at a threaded fitting even though everything is tight. When removed, the ring is hard and brittle instead of soft. It shows visible flattening – the round cross-section has turned into an oval. Or it tears as you pull it off, which answers the question by itself.
At a glance
| Type |
O-ring made of EPDM |
| Location |
Sealing point inside the machine; our documentation does not state the exact position |
| Fits |
Order by part number; our documentation does not name a specific model |
| Scope of delivery |
1 O-ring |
| Part number |
H.1.051 |
| Version |
Cross-section 1,78 mm, inner diameter 10,82 mm, EPDM, hardness 70 ShA |
| Installation |
Fitting by a qualified technician recommended |
| Brand |
La Marzocco |
Important for installation
This ring sits inside the machine, usually at a pressurised threaded fitting. The machine must be depressurised beforehand, and a leak test is part of the job after installation. We deliberately do not provide step-by-step instructions: which fitting can be opened and which cannot is for the person who knows the machine to decide. If in doubt, the work belongs in a workshop.
Who it is for
For service companies and for anyone who orders by part number – for example because H.1.051 is listed in the service documentation. It makes sense to buy O-rings of this size in small quantities to keep in stock: they cost next to nothing and are always missing on a Saturday morning.
What goes with it
From the same number series come the O-ring 1,78 × 11,89 mm made of FKM and the O-ring 1,78 × 20,35 mm made of EPDM – similar cross-section, different diameters, different numbers. For lever machines there are also the O-rings for the LEVA in six sizes. The entire range of seals can be found in the Original spare parts section, and the rest of the brand’s range in the La Marzocco accessories and spare parts section.
From our workshop in Bern and Zurich: We don’t sort new O-rings into a drawer but into labelled little bags with the part number on them. With a 1,78 mm cross-section, three different rings look identical in a loose pile, and the wrong one almost fits during installation – which is the worst of all possibilities. This is our own routine, not a manufacturer’s requirement. After a round of seal replacements, we pull a Nutty Delight as a check, because it reliably tastes the same, which makes it easy to taste any changes in the machine. If you like, try the Cozy Chocolate; you’ll find everything else 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 once they have been installed or test-fitted on a machine. So before ordering, check the model, year of manufacture and serial number of your machine – or drop us a line and we’ll work out the fit together. Your statutory rights regarding defective goods remain unaffected.
Frequently asked questions
Where does this O-ring sit?
Our documentation lists it as item H.1.051, without an installation location. We won’t make one up. Write and tell us where the number appears in your service documentation, and we’ll work out together where it belongs.
What does 70 ShA mean?
That is the hardness of the material, measured in Shore A. 70 ShA is the usual value for seals in hot water: firm enough for pressure, soft enough to seal.
Is EPDM the same as Viton?
No. EPDM and FKM, often called Viton, are two different materials that behave differently. So always use the number from the documentation rather than the first ring that happens to have the same dimensions.
Do I get several pieces?
The price is per piece. Order the quantity you need; for a service stock, drop us a line and we’ll sort out larger quantities.
Can I see the part at your shop?
Yes. Visit our showroom in Bern at Gerberngasse 44 or in Zurich at Hagenholzstrasse 50b. Bring the old ring along and we’ll measure it together.
Unsure about the number? Write to us at [email protected]. We deliver across Switzerland and to Liechtenstein in 2-4 working days.
