Espresso Machine Group Head Gasket Replacement Guide (Breville BES870, Gaggia Classic Pro, DeLonghi Dedica)

Who Gets to Change the Gasket Depends on the Brand

Coffee running down the outside of the portafilter is the classic sign of a worn group head gasket, but check the cheap causes first: grounds on the basket rim, a portafilter not turned fully home, or too much coffee. All three manuals list those. After that, they split sharply on who should replace the gasket:

• Breville expects owners to do it. The Barista Touch (BES880) book gives the full shower screen and silicone seal replacement, and the Barista Express (BES870) book shows the shower screen removal and sends you to Breville for the seal.
• De'Longhi doesn't. The Dedica and La Specialista manuals say: "Have the espresso boiler gasket replaced by Customer Services."
• Gaggia's Classic Pro manual asks you to check the seal isn't dirty, and gives no replacement steps.

The Barista Express's own leak causes are in our Barista Express leaking guide.

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Try This First

• Wipe the basket rim clean of grounds before locking in.
• Turn the handle fully into the group head until you feel firm resistance.
• Use less coffee. An overfilled basket keeps the portafilter from sealing.
• Look at the seal inside the group head. Gaggia's first check is that it isn't dirty.
• Note how far the handle turns. A handle that now swings further than it used to suggests a tired seal (Breville).

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Is It the Gasket?

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Tools and Parts

⚠️ Safety: the group head is very hot after use. Switch off, unplug, and let the machine cool before touching the shower screen. Release any steam first. Don't open the housing: the gasket sits behind the shower screen, and nothing beyond that is an owner part.

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Step 1: Fix the Leaks That Aren't the Gasket

Every manual lists these first.

1. Clean the basket rim. Breville: "Clean excess coffee from the rim of the filter basket to ensure a proper seal in group head." Gaggia: no coffee residue on the edge of the filter holder.
2. Dose correctly. Breville and De'Longhi both list too much coffee. On the Dedica, "too much coffee" is also why the filter holder won't attach.
3. Lock it fully. Breville: rotate until resistance is felt. De'Longhi Dedica: "rotate firmly as far as it will go".
4. Dual Boiler (BES920): dry the rim and the portafilter lugs. Its book lists a wet rim or wet lugs as a cause, and says rotating past center "will not damage the silicone seal".

Time: 2 minutes
Cost: Free
Difficulty: Easy

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Step 2: Clean the Seal and Shower Screen

Gaggia's leak row ("excessive loss of water from the filter holder") includes "the seal is not dirty". Breville's books have you wipe the group head and shower screen after each use and purge it with an empty basket.

1. With the machine cool, wipe the group head interior and the seal with a damp cloth.
2. Lock in the portafilter with an empty basket and run water through briefly to rinse.
3. Gaggia: if brewing is off, the manual also says to immerse the filters in boiling water for 10 minutes, then rinse.

Time: 5 minutes
Cost: Free
Difficulty: Easy

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Step 3: Replace the Breville Silicone Seal

The Barista Express book says: "Over time, the silicone seal surrounding the shower screen will need to be replaced." The Barista Touch (BES880) book prints the full procedure:

1. Press POWER to switch off, and unplug. Let it cool.
2. Carefully remove the water tank and drip tray.
3. Clean the centre of the shower screen screw with a skewer.
4. Loosen the screw counter-clockwise. BES880: flat-head screwdriver. BES870: the short end of the supplied Allen key.
5. Remove the screw and the stainless steel shower screen. Note which side faced down, then wash and dry it.
6. BES880: remove the silicone seal with your fingers or long-nose pliers. Insert the new seal flat side first, so the ribbed side faces you.
7. Refit the shower screen and screw: 2-3 turns by hand, then tighten until flush. "Do not overtighten."
8. Refit the drip tray and tank. Pull a shot and check the edges.

Time: About 30 minutes, plus cooling
Cost: The price of a seal from Breville
Tools: Allen key or flat-head screwdriver, skewer, long-nose pliers
Difficulty: Moderate

Get the seal from Breville. Both books say: "Contact Breville Consumer Support or visit the Breville webpage for replacement silicone seals or for advice." The BES870 book shows how to remove the shower screen but doesn't describe fitting the seal, so ask Breville when you order. 1-866-BREVILLE (1-866-273-8455) in the U.S.

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Step 4: De'Longhi and Gaggia: Use Customer Services

De'Longhi Dedica (EC685, EC695, EC785) and La Specialista: the troubleshooting row "The espresso coffee drips from the edges of the filter holder rather than the holes" lists four causes. The filter holder is incorrectly inserted or dirty, the spout holes are blocked, the filter is blocked, or "the espresso boiler gasket has lost elasticity or is dirty". The remedy for the last one is: "Have the espresso boiler gasket replaced by Customer Services." The manuals give no owner steps, part number or size.

Gaggia Classic Pro: the manual checks the seal is clean and gives no replacement procedure. For service: "contact your local dealer or an authorized service center", using the warranty booklet or gaggia.com.

1. Rule out Step 1 and Step 2 first.
2. Contact De'Longhi customer services, or a Gaggia dealer or service center.

Time: A phone call
Cost: Depends on warranty
Difficulty: Easy

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Model Differences

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Test Before You Trust It

After fitting a new Breville seal, or cleaning any seal:

1. Lock in the portafilter until you feel firm resistance.
2. Pull a normal shot, and watch the portafilter edges for the whole extraction.
3. If coffee still escapes, repeat Step 1. Then contact the manufacturer.

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When DIY Won't Work

Contact the manufacturer if:

• It still leaks around the portafilter with a new seal, a clean rim and a correct dose
• The shower screen screw won't come out, or the screen is damaged
• Water leaks from the group head with no portafilter in
• Your machine is a De'Longhi or Gaggia and the seal is the cause: that's their service job

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Prevent Gasket Leaks

• Wipe the rim every shot. It's in every manual.
• Wipe the group head and seal after each session, and purge with an empty basket.
• Don't overfill the basket. Trim with the Razor (Breville) or use the supplied measure (De'Longhi).
• Don't leave the portafilter locked in when not brewing if your manual says so: the Mr. Coffee Café Barista manual warns it harms the seal.

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FAQ

How do I know if my group head gasket is worn?

Breville's sign is that the portafilter no longer secures properly in the group head: it turns further than it used to, and coffee leaks around the edge even with a clean rim and the right dose. Rule out grounds on the rim and overfilling first.

Can I replace the gasket on a De'Longhi Dedica myself?

The Dedica manual doesn't give owner steps. Its troubleshooting row says to "have the espresso boiler gasket replaced by Customer Services". It lists other causes of the same leak first: the filter holder inserted wrongly or dirty, and blocked holes or filters.

Which way does the new Breville seal go in?

The Barista Touch book says to insert it flat side first, so the ribbed side faces you. Then refit the shower screen and screw, hand-tight for 2-3 turns before tightening until flush. Don't overtighten.

What size gasket does my machine need?

None of these manuals prints a gasket size or part number. Order through Breville Consumer Support or breville.com, or ask De'Longhi or Gaggia service, and give them your model number.

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Related Guides

• Barista Express Leaking Water?: the BES870's three leak causes
• De'Longhi Dedica Not Working?: the Dedica's lights and leak rows
• Gaggia Classic Pro Leaking?: Gaggia's water-loss rows
• Espresso Machine Steam Wand Seal Replacement: leaks at the steam wand

Sources: Breville Barista Touch BES880, Barista Express BES870 and Dual Boiler BES920 instruction books; De'Longhi Dedica EC685/EC695/EC785 and La Specialista instructions; Gaggia Classic Pro RI9380 operating instructions; Mr. Coffee Café Barista BVMC-ECMP1000 user manual.