Pressurized vs Non-Pressurized Portafilter: Complete Grind Size Guide

The pressurized portafilter grind size is different from the non-pressurized grind size. Use the wrong one and your espresso either chokes (nothing comes out) or gushes (watery and sour). This guide explains exactly which grind size works for each type, why they are different, and what goes wrong when you get it wrong. If you own the InstaCuppa 3-in-1 or any home espresso machine, this is essential reading.

What Is a Pressurized Portafilter?

A pressurized portafilter has a double wall with one small hole at the bottom. It creates artificial pressure even if your grind is not perfect.

Look at the bottom of your portafilter basket. If it has a single small hole (about 1mm), it is pressurized. Also called a "double wall" basket. Water passes through the coffee, then squeezes through this tiny hole. That restriction creates back-pressure, which helps produce crema even with an imperfect grind.

This is what makes pressurized baskets beginner-friendly. The small hole does the work of creating pressure. Your grind size, dose, and tamp do not need to be exact. The machine compensates for your mistakes. The InstaCuppa 3-in-1 comes with a pressurized basket for this reason.

What Is a Non-Pressurized Portafilter?

A non-pressurized portafilter has a single wall with many small holes. The coffee puck itself must create all the resistance. Your grind has to be exact.

If the bottom of your basket has dozens of tiny holes (like a shower head), it is non-pressurized. Also called a "single wall" basket. Water passes through the coffee and directly out. There is no restriction valve to help. The coffee puck is the only thing slowing the water down.

This means your grind size must be dialled in precisely. Too coarse and water rushes through (under-extraction, sour, watery). Too fine and water cannot pass through at all (over-extraction or a choked machine). Non-pressurized baskets give better espresso once you learn the skill, but they punish beginners.

What Grind Size for Pressurized Portafilter?

Medium-fine, like table salt. Pressurized baskets work with a range from medium to fine. Pre-ground espresso coffee works well.

The sweet spot is medium-fine. If your shot takes 25 to 30 seconds for 30ml, you are in the right range. If it takes less than 15 seconds, go finer. If nothing comes out or it takes over 45 seconds, go coarser.

What Grind Size for Non-Pressurized Portafilter?

Fine, between table salt and powdered sugar. The window is narrow. You need a good burr grinder to hit it consistently.

The target is a 25 to 30 second extraction for a 30ml shot (1:2 ratio). Adjust grind by tiny amounts. One click on your grinder finer or coarser. Then test. Repeat until you hit the target. This process is called "dialling in." Read our espresso ratio guide for the full process.

What Happens When You Use Too Fine a Grind in a Pressurized Basket?

The machine chokes. No coffee comes out. Or it drips so slowly that what does come out is extremely bitter.

Here is why. A pressurized basket already has a tiny hole that restricts flow. If you also use an espresso-fine grind, you create double restriction. The coffee puck slows the water. Then the tiny hole slows it even more. The pump cannot push water through fast enough. Pressure builds, the safety valve may activate, and you get no coffee or a few drops of bitter liquid.

The fix is simple: go coarser. Switch from fine to medium-fine. If you are using pre-ground espresso coffee and your machine chokes, the pre-ground may be too fine for your pressurized basket. Try a medium grind instead.

What Happens When You Use Too Coarse a Grind in a Non-Pressurized Basket?

Water rushes through in 5 to 10 seconds. The espresso is sour, watery, and has no crema. Under-extraction.

A non-pressurized basket has no valve to slow the water. If the coffee puck is too coarse, water finds easy paths through the gaps between particles. It flows through without extracting enough flavour. The shot pours too fast, looks pale and thin, and tastes sour or acidic.

The fix: grind finer in small steps. One click at a time on your grinder. Each adjustment changes the extraction by a few seconds.

Which Portafilter Type Is Better?

Pressurized is better for beginners. Non-pressurized is better for experienced users. Both make good espresso.

Choose pressurized if: You are new to espresso, you use pre-ground coffee, you do not own a good grinder, or you want consistency without fuss. The InstaCuppa 3-in-1 comes with a pressurized basket.

Choose non-pressurized if: You own a burr grinder, you enjoy dialling in shots, and you want the best possible crema and flavour. Non-pressurized baskets reward skill with better extraction.

Many people start with pressurized and switch to non-pressurized later as they learn. Some machines (not the 3-in-1) let you swap baskets. This gives you a growth path from beginner to intermediate without buying a new machine.

Does Tamp Pressure Matter?

With pressurized baskets: barely. With non-pressurized: yes, about 15kg of even pressure.

In a pressurized basket, the tiny exit hole controls most of the back-pressure. Your tamp affects the shot very little. Just press down enough to make the coffee flat and level. Do not worry about exact pressure.

In a non-pressurized basket, your tamp is part of the resistance equation. Too light and water channels through weak spots. Too hard and the puck chokes. The standard is about 15kg of downward pressure, applied evenly across the surface. Use a calibrated tamper or practice on a bathroom scale to learn the right pressure.

Quick Reference: Grind Size Cheat Sheet

When in doubt, start coarser than you think and go finer one step at a time. It is easier to fix under-extraction (coarse) than over-extraction (fine) because a choked machine needs disassembly and cleanup.

Read more: Pressurized vs Non-Pressurized: Which Needs a Better Grinder? | Espresso Grind Size Guide

Frequently Asked Questions

What grind size should I use with a pressurized portafilter?

Medium-fine, like table salt. Pressurized baskets are forgiving. They work with a range from medium to fine. Avoid espresso-fine grind because it chokes the machine.

What grind size for a non-pressurized portafilter?

Fine, like powdered sugar but not quite flour. The coffee puck itself must create the resistance, so grind size needs to be exact.

Why does my espresso machine choke with no coffee coming out?

Your grind is too fine for a pressurized portafilter. The double wall plus the fine grind creates too much resistance. Use a coarser grind.

Can I use pre-ground coffee in a pressurized portafilter?

Yes. Pre-ground espresso coffee works well in pressurized baskets because they are forgiving about grind size.

Does the InstaCuppa 3-in-1 have a pressurized or non-pressurized portafilter?

Pressurized (double wall). This means it is beginner-friendly and works with pre-ground coffee and medium-fine grinds.