A pressurised basket has a built-in way to slow the water. An unpressurised basket leaves that job to the coffee. That one difference drives most of what follows.
The two types in plain words
A pressurised basket is also called dual-wall or double-walled. It has an inner wall with many holes and an outer wall with a single small hole at the base. That small hole "is meant to create back pressure"1. Back pressure is pressure pushing against the flow of water.
An unpressurised basket, also called non-pressurised or single-wall, has holes covering the entire base1. There's no second wall to slow things down.
One maker describes its pressurised filters as designed to "intentionally slow the water" flow during extraction2. Of its unpressurised filters it says they "provide no additional slowing of the water" flow2.
Side by side
| Pressurised | Unpressurised | |
|---|---|---|
| Other names | Dual-wall, double-walled1 | Single-wall, non-pressurised1 |
| Holes | Small outlet hole in the outer wall1 | Holes across the whole base1 |
| Effect on flow | Built to slow the water2 | No extra slowing2 |
| What you adjust | Less depends on grind and tamp3 | Grind, amount and tamp all need experimenting2 |
Who each one suits
Pressurised. The maker's blog says these baskets are generally better for beginner espresso brewers1. One manual says its dual-wall baskets suit pre-ground coffee and help the extraction "regardless of the grind, dose, tamp pressure or freshness"3.
Unpressurised. The same manual says its single-wall baskets suit freshly ground whole beans3. The product text adds that experimentation with grind size, grind amount and tamp force is required to get good results2.
So the choice isn't about one being better. It's about how much you want to control, and what coffee you have on hand.
How to tell which you have
Start with the manual. Look for the section on filter baskets or accessories. One maker's product text lists two pairs of filters, each labelled by type: "Pressurized" dual-wall and "Non-Pressurized" single-wall. A machine can ship with both2.
Then look at the underside of the basket. Many holes across the base point to unpressurised. A single small outlet in the outer wall points to pressurised1. The blog adds that some pressurised baskets have a few small holes at the base, but always many fewer than the other piece (it says "outer piece")1.
For markings and manual wording, there's a separate identification guide.
Can you swap them?
Sometimes. The maker's blog says that in many cases you can switch between a pressurised and unpressurised basket1. It also warns that some machines are meant to be used with just one type1.
Don't guess. If your manual doesn't list the other type, treat your machine as built for the one it came with. Check with the maker before fitting anything else.
Where the facts come from
- Pressurized vs. non-pressurized baskets, Breville
- Breville BES830XL product resources, Seattle Coffee Gear (reproducing the maker's product text)
- Breville BES870XL manual, selecting a filter basket, Breville (via ManualsOnline)
More on baskets
What a Portafilter Basket DoesWhat the basket inside an espresso portafilter is for, and how its design shapes the way water moves through the coffee.
Single-Wall and Double-Wall BasketsWhat single-wall and double-wall mean for an espresso basket, how the two are built, and which coffee each is meant for.
Basket Sizes and Dose RangeHow an espresso basket's size, its stated dose range and the coffee you put in relate, using a maker's own manual as the guide.