Last updated: October 2, 2026
The Breville Dual Boiler is built around a commercial-style 58 mm portafilter, so its group head gasket is not the same part used by many Breville machines with smaller portafilters. If your BES920 is leaking around the portafilter, the group gasket is the first part to inspect—but it is not the only possible cause.
A worn gasket can cause water to escape at the edge of the basket, leave a wet mess under the group head, or make the portafilter increasingly difficult to lock into position. The right replacement depends on which seal is failing, whether your machine is a BES920 or a related regional version, and whether you want an exact replacement or a longer-lasting aftermarket option.
Which Breville Dual Boiler gasket do you need?
Most owners asking about a “Breville Dual Boiler gasket” mean the group head gasket: the rubber seal that sits above the shower screen and seals against the portafilter rim. It is a thick, circular seal exposed to heat, coffee oils, and repeated locking pressure.
There are also smaller seals inside the machine. O-rings may be used around steam-valve components, water connections, the hot-water outlet, and boiler fittings. Those parts are not interchangeable with the group gasket. If the leak is inside the case, replacing the group seal will not solve it.
Before ordering, check the model label and compare the replacement with the old part. Search using the full model number, such as BES920XL or the equivalent model sold in your country. A useful starting point is this selection of Breville Dual Boiler group head gaskets, but verify the listing’s compatibility rather than relying only on a photograph.
Signs your group gasket is worn
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- Water sprays or drips around the portafilter during brewing.
- The portafilter must be turned farther than usual to seal.
- The handle feels unusually loose or unusually hard to lock.
- The gasket has flattened, hardened, cracked, or developed a shiny compressed surface.
- Cleaning the shower screen and portafilter does not stop the leak.
A leak does not always mean the gasket is bad. Coffee grounds on the portafilter rim, a damaged basket, a bent portafilter, or a blocked shower screen can also prevent a proper seal. Clean the mating surfaces first. If the leak remains with a clean basket and portafilter, the gasket becomes the likely culprit.
Original, aftermarket, or silicone?
An original-equipment replacement is usually the safest choice when you want the same fit and feel as the factory part. It is particularly sensible if the machine is still under warranty or you are repairing it for resale. The disadvantage is availability: Breville parts can be region-specific, and some listings bundle the gasket with a shower screen or other parts you do not need.
Aftermarket rubber gaskets cost less and are often perfectly adequate. The important details are the outer diameter, inner opening, thickness, profile, and material—not simply the claim that a gasket is “58 mm.” Several espresso machines use 58 mm portafilters but have different group-gasket dimensions or profiles.
Silicone gaskets are a popular upgrade. They are generally more resistant to heat and can remain flexible longer than ordinary rubber. They may also be easier to remove during the next service because they are less likely to harden in place. The trade-off is fit: a silicone gasket that is slightly too thick can make the portafilter difficult to lock, while an incorrect profile can leak despite looking suitable.
| Option | Advantages | Drawbacks | Best for |
|---|---|---|---|
| Original-equipment rubber | Most predictable fit; factory-style feel | Can be harder to source; may cost more | Warranty repairs and owners who want a direct replacement |
| Compatible rubber aftermarket | Low price; easy to buy; usually adequate | Quality and dimensions vary between sellers | Routine maintenance on an older machine |
| Compatible silicone | Flexible, durable, and often easier to remove later | Fit can be fussy; may feel different when locking | Frequent users who want a longer-service-life seal |
For most home users, the cheaper compatible rubber gasket is fine if the dimensions are confirmed and the seller identifies the BES920 or the exact machine variant. Paying more for silicone makes more sense if you brew several times a day, replace seals regularly, or dislike seals that become brittle and stuck.
How to replace the Breville Dual Boiler group gasket
Unplug the machine, let it cool completely, and remove the portafilter and shower screen. The shower screen is normally held by a central screw. Keep the screw and screen together so they return in the same order.
Use a blunt plastic pick or a small flat tool carefully at the edge of the old gasket. Avoid digging into the group-head metal or scratching the sealing surface. If the gasket is hard, it may come out in pieces. Remove every fragment, then wipe away coffee oil and residue with a damp cloth.
Press the new gasket into its groove with the correct face oriented upward. Some gaskets have lettering or a shaped profile that indicates orientation; follow the seller’s or manufacturer’s instructions. Reinstall the shower screen and screw, but do not overtighten it.
Run water through the group without coffee, then lock in an empty portafilter. It should seal without excessive force. If the handle stops far earlier or later than before, do not force it. The gasket may be the wrong thickness, installed upside down, or not fully seated.
A small amount of food-safe espresso-machine lubricant is not normally required on the group gasket itself. Lubricant can attract coffee residue and make the seal slippery. Clean water and a correctly fitted gasket are usually all that is needed.
Useful tools and maintenance supplies
A replacement gasket is easier to fit with a blunt pick, a clean cloth, and the correct screwdriver for the shower-screen screw. A dedicated espresso gasket removal tool can help if the old seal is stuck, but it is not essential for a routine replacement.
Keep the portafilter rim, basket edge, and group gasket clean. After brewing, wipe the underside of the group head and run a short flush. During backflushing, use only a cleaner suitable for espresso machines and follow the Breville instructions. Excess chemical residue or aggressive scraping can shorten the life of seals.
If water is leaking from beneath the machine, from the side panels, or near a valve, stop treating it as a simple gasket replacement. Internal leaks may involve pressurized water, hot surfaces, or electrical components. A qualified appliance or espresso-machine technician is the safer option, especially if the machine trips a breaker or shows signs of overheating.
What to check before buying
- Confirm the exact Dual Boiler model and regional suffix.
- Check that the listing specifically states compatibility, not just “58 mm.”
- Compare the gasket’s thickness and profile with the old seal if dimensions are provided.
- Buy a two-pack only if the price is sensible; a spare is useful, but seals do not need frequent replacement.
- Read recent reviews for reports of portafilter fit and leakage, not just claims about material.
If you are also servicing the machine, a compatible 58 mm shower screen can be considered when the existing screen is warped, badly clogged, or permanently stained. Do not replace it automatically: a sound screen can usually be cleaned and reused.
FAQ
Is the Breville Dual Boiler gasket 58 mm?
The Dual Boiler uses a 58 mm portafilter, but “58 mm” alone does not guarantee the correct gasket. The gasket’s thickness and profile must also match the group head.
How often should I replace the gasket?
Replace it when it leaks, hardens, cracks, or no longer seals correctly. A home machine may go years between replacements, while a heavily used machine may need one sooner.
Can I replace the gasket without opening the machine?
Yes. The group head gasket is an external service part and can normally be replaced after removing the shower screen. Internal O-rings and boiler seals are different repairs.
Why does my new gasket still leak?
Check for coffee grounds, a damaged basket, an incorrectly seated gasket, or an incompatible thickness. If the leak is inside the case or comes from a valve, the group gasket is not the right repair.
