What is a dual boiler?
An espresso machine heats water for two different jobs. Espresso needs water at a precisely set temperature, while steaming milk needs pressurised steam, which means a much higher temperature. A dual boiler splits these jobs: one boiler heats water for coffee, the other produces steam.
What it means behind the bar: the barista can pull espresso and steam milk at the same time without one throwing off the other. Coffee temperature is set independently of steam. When you sell a lot of cappuccinos and lattes, this is the basis of consistency.
All the La Marzocco machines we offer have a separate coffee boiler and a separate steam boiler. The boilers are made of AISI 316L stainless steel and hand-welded using the TIG method.
What about a heat exchanger?
In other machines you will find a single boiler with a heat exchanger: the boiler produces steam, and the brewing water heats up as it flows through a tube running through that boiler. It is a simpler design, but the brewing water temperature then depends on how the steam boiler is working and how often the barista brews. None of the La Marzocco machines we offer has a heat exchanger.
What is a saturated group?
The group is the part you lock the portafilter into and through which water passes through the coffee. In a saturated group, the group is connected directly to the coffee boiler and water circulates through it constantly. The group therefore has the same temperature as the boiler, with no heating up or cooling down between shots.
La Marzocco patented this design in 1970 in the GS model, whose name comes from the Italian Gruppo Saturo. The temperature difference between consecutive shots is below 0.5°C.
What it means in the cup: the first espresso in the morning and the hundredth at peak time are brewed at almost the same temperature, so the taste stays consistent all day.
Dual PID and insulated boilers
PID is an electronic controller that drives the heating element so that the boiler temperature stays stable instead of swinging between on and off thresholds. Dual PID means separate temperature control for the coffee boiler and the steam boiler. On the Strada, temperature is controlled separately on each group.
Insulated boilers lose less heat. They use less energy and keep the temperature more stable throughout the working day. All the models we offer have them.
What do independent boilers per group give you?
In a machine with independent boilers, each group has its own coffee boiler. You set the temperature separately on each group, so you can brew a light roast from one roastery and a darker one from another at the same time, each at its own temperature.
Independent boilers are found on the Linea PB X, GB5 X, KB90, Strada S, Strada X and Leva X. On the Linea PB X and GB5 X this applies to the 2- and 3-group versions. The 4-group versions have two coffee boilers of 3.4 l each.
Do you brew coffees from several roasteries? Let us check whether independent boilers make sense in your venue.
Boiler layout in La Marzocco machines
| Model | Groups | Dual boiler | Saturated groups | Independent boilers per group | Coffee boiler |
|---|---|---|---|---|---|
| Linea Classic S | 1–4 | yes | yes | – | 1.8 / 3.4 / 5 / 2 × 3.4 l |
| Linea PB | 2–4 | yes | yes | – | 3.4 / 5 / 2 × 3.4 l |
| Linea PB X | 2–4 | yes | – | yes (2- and 3-group) | 2 × 1.3 / 3 × 1.3 / 2 × 3.4 l |
| KB90 | 2–4 | yes | – | yes | 2 × 1.3 / 3 × 1.3 / 4 × 1.3 l |
| GB5 S | 2–4 | yes | yes | – | 3.4 / 5 / 2 × 3.4 l |
| GB5 X | 2–4 | yes | – | yes (2- and 3-group) | 2 × 1.3 / 3 × 1.3 / 2 × 3.4 l |
| Strada S | 2 or 3 | yes | yes | yes, PID on each group | 2.6 / 3.9 l |
| Strada X | 1–3 | yes | yes | yes, PID on each group | 1.3 / 2.6 / 3.9 l |
| Leva S | 2 or 3 | yes | yes | – | 3.4 / 5 l |
| Leva X | 2 or 3 | yes | yes | yes | 2 × 1.3 / 3 × 1.3 l |
Who is fine with a dual boiler, and when do you need independent boilers?
A dual boiler with saturated groups is enough for most cafés, restaurants and hotels. If you serve one espresso coffee, perhaps a decaf, and classic milk drinks, the Linea Classic S or Linea PB will give you a stable temperature with no extra handling.
Independent boilers make sense when you change coffees often, serve several roasteries at once or your baristas want to match the temperature to a specific coffee. This is typical of a specialty café and a roastery with a bar.
Samuel Pilichowski, barista trainer and founder of Colbergcoffee, puts it plainly: every specialty café should have at least a dual boiler. That is the baseline we start from when choosing a machine. Read more about choosing a model in the guide Which espresso machine for a café? and in our comparison of the Linea Classic S, Linea PB, KB90 and Strada.
frequently asked questions
How does a dual boiler differ from a heat exchanger?
A dual boiler has separate boilers for coffee and steam, so the coffee temperature is set independently of the steam. In a heat exchanger, the brew water is heated in the steam boiler, so its temperature depends on how the steam boiler is working. The La Marzocco machines we offer have separate coffee and steam boilers.
What does a saturated group give you?
A stable temperature at the group. The group is connected to the coffee boiler and water circulates through it constantly, so consecutive espressos brew at almost the same temperature, with a difference of less than 0.5°C.
Does every café need independent boilers?
No. They are useful when you brew several coffees at different temperatures. With one espresso coffee, a dual boiler with saturated groups is enough, as on the Linea Classic S or Linea PB.
Which La Marzocco machines have independent boilers per group?
Linea PB X, GB5 X (in 2- and 3-group versions), KB90, Strada S, Strada X and Leva X.
What does dual PID mean?
Separate electronic temperature control for the coffee boiler and the steam boiler. The temperature stays stable and the barista can set it precisely.
read also
- Linea Mini or GS3? Which one for your home?
- Which espresso machine for an office? Does a traditional one make sense?
- Linea Micra or Linea Mini? Which one for your home?
- Grind-by-Sync: how La Marzocco controls a Mahlkönig grinder
- How to make milk drinks faster in a café
- Espresso machine for a roastery or showroom: how to show off your coffee
- 10 mistakes when buying a café espresso machine (and how to avoid them)
- Espresso machine for a bakery or patisserie: selling coffee alongside your bakes
- Is a more expensive café espresso machine worth it?
- New espresso machine in your café: a barista training plan for the first month
- Espresso grinder for a café: on-demand or doser, and how many you need
- ABR drip tray scales or AV dosing? When the extra cost pays off
- Espresso machine service: what it covers, how often, and when to call a technician
- Café espresso machine leasing: lease, rent or buy?
- La Marzocco in Warsaw: Tekla, Doza and Wandal
- Specialty café: which espresso machine to choose? What a specialty café needs
- Opening a café? An equipment plan, step by step
- When to replace your café espresso machine? 5 signs
- Water for espresso machines in venues: hardness, filtration, boiler protection
- Espresso machine cleaning and backflush: a schedule for your team
- Espresso machine for a restaurant or hotel: what to look for
- Which espresso machine for a café? A guide to La Marzocco machines
- Linea Classic S, Linea PB, KB90 or Strada? A comparison
- AV, ABR, EE, MP: what La Marzocco machine versions mean
- Preparing your venue for an espresso machine: power, water, drain
- How many groups does your venue need?