När vi väl är hemma, kan vi slappna av och dricka te.

In this sentence, väl adds emphasis and means something like once, finally, or when we’re actually.

So När vi väl är hemma is not just When we’re home, but more like:

• Once we’re finally home
• When we’re at home at last

It gives a feeling of relief or of reaching that point.

Because Swedish main clauses follow the V2 rule: the finite verb normally comes in the second position.

Here, the whole clause När vi väl är hemma comes first. After that, the main clause must begin with the finite verb:

• När vi väl är hemma, kan vi slappna av ...

Not:

• När vi väl är hemma, vi kan ...

This is very common in Swedish when a time phrase or subordinate clause comes first.

Because När vi väl är hemma is a subordinate clause, and in Swedish subordinate clauses, sentence adverbs often come before the finite verb.

So:

• vi väl är hemma

rather than the main-clause pattern:

• vi är väl hemma

This is an important difference between main clauses and subordinate clauses in Swedish.

Hemma means at home — a location or state.

Hem means home in the sense of to home / homeward — a direction.

So:

• är hemma = are at home
• går hem = go home
• kommer hem = come home

In this sentence, the idea is that we are already there, so hemma is correct.

Because the sentence talks about the time after arriving, not the journey itself.

• När vi väl är hemma = Once we are home / once we’re at home
• När vi väl kommer hem = When we get home

Both can work in some contexts, but är hemma focuses on the state of being home, which fits well with relax and drink tea.

Because kan is a modal verb, and modal verbs in Swedish are followed by the infinitive without att.

So you say:

• kan slappna av
• kan dricka

not:

• kan att slappna av
• kan att dricka

Other Swedish modal verbs work the same way, such as vill, ska, måste, and får.

Because slappna av is the full verb expression meaning relax.

The little word av is part of the verb, much like a particle in English phrasal verbs.

Examples:

• Jag behöver slappna av. = I need to relax.
• Nu kan vi slappna av. = Now we can relax.

So slappna by itself is not what you normally use here.

Because one modal verb can apply to more than one infinitive.

So:

• kan vi slappna av och dricka te

means:

• we can relax and drink tea

The kan covers both slappna av and dricka. English works the same way:

• We can relax and drink tea

Swedish often uses the present tense for future meaning when the context makes the time clear.

So:

• När vi väl är hemma, kan vi slappna av ...

can refer to a future situation, even though the verbs are present tense.

English does something similar in clauses with when:

• When we get home, we can relax.

So this is very natural Swedish.

The comma after hemma is possible, but in modern Swedish it is often optional.

You may see both:

• När vi väl är hemma, kan vi slappna av och dricka te.
• När vi väl är hemma kan vi slappna av och dricka te.

The comma can make the sentence easier to read, especially after a longer introductory clause, but many writers leave it out.

Yes. You could say:

• När vi är hemma, kan vi slappna av och dricka te.

That is grammatical, but it is more neutral.

Adding väl gives extra nuance: it suggests once we’re finally home or when we’ve at last gotten home. So väl adds feeling, not basic meaning.

Here när is a subordinating conjunction meaning when.

It introduces the subordinate clause:

• När vi väl är hemma

Then the main clause follows:

• kan vi slappna av och dricka te

So när is not acting as a question word here; it is linking two parts of the sentence.