Replacing the Silicone Gasket: Fixing Leaks from the Group Head

Water dripping from around your portafilter? Difficulty locking the portafilter at 6 o’clock? You likely need a new group head gasket. This silicone seal wears out over time—typically every 6-12 months with regular use—and replacing it is a simple DIY task.

Here’s everything you need to know about diagnosing, replacing, and maintaining your Breville group head gasket.

Why Gaskets Fail

Normal Wear

The silicone gasket sits between your portafilter and the group head, compressed every time you lock in. Over time:

1. Heat cycles cause expansion and contraction
2. Coffee oils degrade the silicone
3. Compression causes permanent deformation
4. Hard water deposits can accelerate wear

Signs You Need a New Gasket

Symptom	What It Means
Water leaking around portafilter	Gasket not sealing
Portafilter won’t lock at 6 o’clock	Gasket too hard/thick
Portafilter locks past 6 o’clock easily	Gasket too worn/thin
Visible cracks in gasket	Definitely needs replacement
Gasket comes out when removing portafilter	Gasket failed

Tools and Materials Needed

Required

• New silicone gasket (8.5mm for most Breville models)
• Flathead screwdriver or gasket removal pick
• Clean cloth

Optional

• Food-safe silicone lubricant
• Hex key (for shower screen removal)
• Espresso machine brush

Step-by-Step Gasket Replacement

Step 1: Prepare the Machine

1. Turn off your Breville and unplug it
2. Wait 30+ minutes for the group head to cool
3. Remove the portafilter

Important: Working on a hot group head risks burns and makes the gasket harder to remove.

Step 2: Remove the Shower Screen

1. Locate the center screw (Phillips or hex, depending on model)
2. Unscrew and remove

3. Carefully remove the shower screen
4. Remove the dispersion plate (metal disc behind screen)
5. Set all parts aside

Step 3: Remove the Old Gasket

1. Look inside the group head—the gasket is the black rubber ring
2. Insert a flathead screwdriver or pick under the gasket edge
3. Work around the circumference, prying gently
4. The gasket should pop out in one piece (or fragments if very old)

Tip: Stubborn gaskets may need working from multiple angles. Be patient—don’t scratch the group head.

Step 4: Clean the Groove

1. Wipe the gasket groove with a clean cloth
2. Remove any debris, coffee residue, or old gasket fragments
3. Inspect for mineral deposits—clean if present
4. Ensure the groove is completely clean and dry

Step 5: Install the New Gasket

1. Check orientation: Most gaskets have a flat side and a lip. For these blue silicone gaskets, the lip typically faces UP (toward the machine).

2. Place the gasket into the groove
3. Press firmly around the entire circumference
4. Ensure it’s seated evenly with no gaps

Optional: Apply a tiny amount of food-safe silicone lubricant to help seating. This also eases future removal.

Step 6: Reassemble

1. Replace the dispersion plate
2. Replace the shower screen
3. Reinstall the center screw
4. Tighten firmly but don’t over-torque

Step 7: Test the Seal

1. Insert your portafilter (empty is fine)
2. Lock it to 6 o’clock position—it should require moderate effort
3. Run water without coffee—check for leaks around the portafilter
4. If no leaks, you’re done!

Testing After Replacement

Lock Position Check

• Locks at 5 o’clock: Gasket may be too thick or installed incorrectly
• Locks at 6 o’clock with firm pressure: Perfect
• Locks past 6 easily: Gasket too thin (wrong size or still worn old gasket)

Leak Check

1. Lock empty portafilter
2. Run group head (brew button without coffee)
3. Watch for drips around portafilter ears
4. Any leakage indicates improper seating—reinstall

First Shot Check

1. Pull a regular espresso shot
2. Watch for leaks during extraction
3. Check shot quality (should be normal)

Choosing the Right Gasket

Breville-Specific Sizing

Model Series	Gasket Size
Barista Express (BES870)	54mm, 8.5mm thick
Infuser (BES840)	54mm, 8.5mm thick
Barista Pro (BES878)	54mm, 8.5mm thick
Dual Boiler (BES920)	58mm, 8.5mm thick

OEM vs Third-Party

OEM Breville gaskets:

• Guaranteed fit
• Higher price ($8-15)
• Available from Breville.com

Third-party gaskets:

• Often identical quality
• Lower price ($3-8)
• Check reviews for your specific model

Silicone vs Rubber

Modern gaskets are silicone, which:

• Lasts longer than rubber
• Handles heat better
• Resists coffee oils
• Remains flexible longer

Frequently Asked Questions

How often should I replace the gasket?

Every 6-12 months with daily use, or when you notice seal issues. Some last longer with gentle care.

Can I use third-party gaskets?

Yes—as long as the dimensions match. Most aftermarket gaskets work identically to OEM.

Why is my new gasket leaking?

Check:

1. Orientation—lip facing the right direction
2. Seating—fully pressed into groove
3. Debris—groove was clean before installing
4. Size—correct dimensions for your model

What’s the correct gasket orientation?

For most Breville gaskets, the beveled edge (lip) faces DOWN toward where the portafilter locks. But check your specific model—some are reversible.

My portafilter still won’t lock properly after replacement

The new gasket may need a few uses to “break in.” If it’s too tight at first, that’s normal. If still problematic after 10-20 uses, verify you have the correct size.

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Related Guides:

• Shower Screen Cleaning
• The Cleaning Cycle Tutorial
• Descaling Guide