La macchina espresso e il gruppo erogatore sono puliti.

Because the subject is two things together:

• la macchina espresso
• il gruppo erogatore

They are joined by e = and, so the subject is plural.
That is why Italian uses the plural form of essere:

• è = is for one thing
• sono = are for more than one thing

So:

• La macchina espresso è pulita. = The espresso machine is clean.
• Il gruppo erogatore è pulito. = The brew group is clean.
• La macchina espresso e il gruppo erogatore sono puliti. = The espresso machine and the brew group are clean.

Because the adjective refers to both nouns together, and one of them is masculine:

• la macchina = feminine
• il gruppo erogatore = masculine

In Italian, when an adjective describes a mixed group containing at least one masculine noun, the adjective normally takes the masculine plural form.

So:

• pulita = feminine singular
• pulito = masculine singular
• pulite = feminine plural
• puliti = masculine plural

Since the subject is mixed (feminine + masculine) and plural, Italian uses puliti.

Because this is a normal structure with essere + adjective.
The adjective comes after the verb and agrees with the whole subject.

So instead of saying:

• La macchina espresso è pulita e il gruppo erogatore è pulito

Italian can combine them into:

• La macchina espresso e il gruppo erogatore sono puliti

This is shorter and very natural.

Macchina espresso is a compact way of saying espresso machine.

In Italian, especially in technical, commercial, or manual-style language, noun combinations like this are common. Here espresso specifies the type of machine.

You may also hear:

• macchina per espresso
• macchina da espresso
• macchina per caffè espresso

These are more expanded versions.
So macchina espresso is understandable and common in product or instruction contexts, even if it feels more compressed.

Not really in the usual sense. Here espresso functions more like a label or type-specifier attached to macchina.

It does not change form to agree with macchina. It stays espresso.

So this is not like a normal adjective such as:

• macchina nuova = new machine
• macchina pulita = clean machine

Instead, espresso is part of the name/type of machine.

It is a technical term for a part of the coffee machine. In espresso-machine language, it usually refers to the brew group or group head, the part that dispenses the coffee.

Breaking it down:

• gruppo = group/unit/assembly
• erogatore = dispenser/delivery unit

So together it means the dispensing/brewing assembly of the machine.

In Italian, when two singular nouns are linked by e, each noun usually keeps its own article.

So:

• la macchina e il gruppo
• not normally la macchina e gruppo

This is standard Italian and sounds natural.

No, that would normally be incorrect here.

Pulite is feminine plural, but the two nouns are not both feminine:

• la macchina = feminine
• il gruppo erogatore = masculine

Because the group is mixed, the adjective becomes masculine plural: puliti.

Yes. You can say:

• La macchina espresso è pulita e il gruppo erogatore è pulito.

This is grammatically correct and may sound clearer if you want to emphasize each item separately.

But the original sentence is more compact and very natural.

The given order is the most neutral and natural:

• La macchina espresso e il gruppo erogatore sono puliti.

Italian can sometimes change word order, but in a normal statement this version is the best one for learners to use.

Because the sentence refers to one machine and one brew group. Each noun is singular on its own:

• la macchina = the machine
• il gruppo erogatore = the brew group

They become plural only as a combined subject, which is why the verb and adjective are plural:

• sono puliti

Yes, depending on context. Pulito basically means clean. In equipment instructions, it often implies that the parts have been properly cleaned and are now in a clean state.

So in this sentence, sono puliti means they are clean.

Then the adjective would usually be feminine plural.

For example:

• La macchina e la tazza sono pulite.

Both nouns are feminine, so the adjective becomes pulite.

But in your sentence one noun is masculine (il gruppo), so the adjective is puliti.