Bialetti Moka Express Gasket: Size and Why It Leaks
Buy the gasket by cup size - 3-cup, 6-cup and 9-cup rings are not interchangeable. Replace roughly every twelve months, and fit the filter plate first, then the ring.
Also sold as: Sold as gasket-only or gasket plus plate multipacks
Does it fit your machine?
Match your model number exactly — the code on the rating label, not the name on the front of the machine.
| Model | Notes |
|---|---|
| Moka Express 3 cup | 3-cup gasket only |
| Moka Express 6 cup | 6-cup gasket only |
| Moka Express 9 cup | 9-cup gasket only |
| Other Bialetti stovetop models | Match the cup number stamped on the base |
Your model is not on this list. Do not assume it fits — send us the model number and we will check it.
OEM or aftermarket?
Gasket and plate set:
Prime Bialetti Moka Express 6 Cup Replacement Filter and 3 Gaskets , White
As an Amazon Associate we earn from qualifying purchases. Product prices and availability are accurate as of the date/time indicated.
A moka pot has one consumable part and this is it. The rubber ring under the rim of the upper chamber seals the two halves against steam pressure. It hardens with heat, loses its squash, and then the pot hisses and spits from the seam instead of pushing coffee up the spout. That is not a broken pot – it is a two-minute part.
Get the size right, and only the size
Bialetti gaskets are sold by cup size, and the sizes are not interchangeable. A 3-cup ring will not seal a 6-cup pot. The cup number is stamped on the base of most pots, and it is also the number in the model name.
Buy the gasket and the filter plate together where you can. The plate is a thin perforated disc that sits above the gasket, and it warps and clogs on roughly the same timescale. Most replacement packs include both because they wear as a pair.
How often
Every twelve months for daily use, or as soon as the ring feels hard and stops springing back when you press it with a fingernail. Signs it is due:
- Steam or coffee escaping the seam while it brews.
- The pot taking noticeably longer to come up.
- Having to overtighten the halves to get a seal.
That last one matters. Overtightening to compensate for a dead gasket is how the aluminium threads get damaged, and that is terminal.
Replacing it
- Let the pot cool completely and unscrew the two halves.
- Prise out the old ring from inside the upper chamber. A hardened one usually needs a fingernail or a blunt plastic tool under the edge.
- Lift out the filter plate and check it. If the holes are blocked or the disc is dished, replace it.
- Fit the plate first, then the gasket over it, pressing the ring evenly into the groove all the way round.
- Assemble hand tight only. A fresh gasket seals with modest pressure. If you need force, the ring is seated wrong.
Making the new one last
Never wash a moka pot in a dishwasher – detergent and heat destroy gaskets fast and strip the aluminium. Rinse with warm water, dry the halves separately, and store the pot unscrewed so the ring is not compressed while it sits.
Why the gasket is the part that ages
A moka pot builds pressure by boiling water in the lower chamber and forcing it up through the coffee bed. The rubber ring under the rim of the upper chamber is what stops that pressure escaping sideways. It is squeezed between two aluminium faces and heated to boiling point every time you use the pot.
Rubber under repeated heat cycling loses its plasticiser and hardens. A hardened ring cannot deform enough to fill the gap, so steam escapes at the seam instead of pushing coffee up the spout — and because the pressure never builds properly, what does come up is weak and slow.
Testing a gasket without taking the pot apart
Press the ring with a fingernail. A healthy gasket dents and springs back. A dead one feels like hard plastic and holds the dent. If you can see cracks along the inner edge, it is well past due.
The other tell is your hands: if you have started tightening the two halves harder than you used to in order to get a clean brew, the gasket has already gone. Overtightening is how aluminium threads get damaged, and stripped threads end the pot.
The filter plate wears at the same rate
The perforated disc that sits above the gasket clogs with fine grounds and coffee oil, and it dishes slightly over years of pressure cycling. A clogged plate slows the brew and pushes more grounds into the cup; a dished one stops the gasket seating flat.
Replacement packs usually include both because they fail together. If yours came as gasket-only and the plate looks dark or uneven, buy the pair.
Size, and why it is not negotiable
Bialetti sells gaskets by cup size — 1, 2, 3, 4, 6, 9 and 12 cup — and they are genuinely different diameters. The number is stamped on the base of the pot and appears in the model name. A ring that is close but not right will either not seat at all or will seat and then extrude under pressure, which is worse because it fails mid-brew.
Care that doubles a gasket’s life
- Never dishwash a moka pot. Detergent strips the gasket and the aluminium’s protective oxide layer at once.
- Rinse with warm water only, and dry the halves separately before storing.
- Store the pot unscrewed. A gasket left compressed between two aluminium faces for weeks takes a permanent set.
- Do not scrub the inside of the lower chamber. The dark patina is normal and protective; scouring it off accelerates corrosion.
Related on BrewerRepair: Breville Water Filter (BWF100) and Breville Portafilter and Breville Espresso Machine Not Building Pressure.
Gasket and filter plate sets
Buy by cup size. Sets including the filter plate are better value because both wear together.
Bialetti Moka Express 6 Cup Replacement Filter and 3 Gaskets , White
Where to buy it
Bialetti
Bialetti Moka Express Gasket: Size and Why It Leaks
Paid link. Price shown is indicative — check the listing for the current price. We earn a commission at no extra cost to you.
Questions about this part
Why does my moka pot leak steam from the middle?
The gasket has hardened and lost its seal. It is a consumable part and needs replacing roughly once a year.
Are Bialetti gaskets one size?
No. They are sold by cup size and a 3-cup ring will not seal a 6-cup pot.
Should I replace the filter plate too?
Yes, if it is dished or the holes are blocked. Most replacement packs include both because they wear together.
Can I put my moka pot in the dishwasher?
No. Detergent and heat destroy the gasket quickly and strip the aluminium.