Det kommer an på om dreneringen virker eller ikke.

It means it depends on.

This is a fixed expression in Norwegian:

• å komme an på = to depend on

So in this sentence:

• Det kommer an på ... = It depends on ...

You usually learn it as a chunk, because the meaning is not completely obvious if you translate each word separately.

Here, det is a dummy subject or formal subject, similar to English it in it depends.

It does not refer to a specific thing. It is just required to make the sentence grammatically complete.

Compare:

• It depends on the weather.
• Det kommer an på været.

So det here works very much like English it.

Because å komme an på is a phrasal/particle-style expression in Norwegian.

Its parts are:

• kommer = present tense of å komme
• an
• på

Together, they form the idiomatic meaning depends on.

In main clauses, Norwegian often splits this kind of expression:

• Det kommer an på ...

But in the infinitive, you usually see the full form together:

• å komme an på noe = to depend on something

So you should learn komme an på as one expression, even though the words can appear separated in a sentence.

Here, om means whether.

So:

• om dreneringen virker eller ikke = whether the drainage works or not

This is a very common use of om in Norwegian.

It can sometimes correspond to English if, but in sentences like this, whether is usually the better explanation:

• I don’t know if/whether it works
  = Jeg vet ikke om det virker

So in your sentence, om introduces an indirect yes/no question.

Because dreneringen is the definite form of the noun.

• drenering = drainage / drainage system
• dreneringen = the drainage / the drainage system

The ending -en marks definiteness for this masculine noun.

So the sentence is talking about a specific drainage system, not drainage in general:

• om dreneringen virker = whether the drainage works

Virker is the present tense of å virke.

In this sentence, it means:

• works
• functions
• possibly is effective

So:

• dreneringen virker = the drainage works

Be aware that å virke can have several meanings depending on context, such as:

• to work / function
• to seem / appear
• to have an effect

Here, the natural meaning is to function properly.

Because after om, you have a subordinate clause, and subordinate clauses in Norwegian do not use the main-clause inversion pattern.

Main clause:

• Dreneringen virker. = The drainage works.

Subordinate clause after om:

• ... om dreneringen virker ...

You keep the normal subject + verb order:

• dreneringen
  • virker

So om virker dreneringen would be wrong here.

Eller ikke means or not.

So:

• om dreneringen virker eller ikke = whether the drainage works or not

This is a very common pattern in Norwegian:

• om ... eller ikke = whether ... or not

It makes the meaning explicit, but sometimes Norwegian can omit eller ikke if the context is clear:

• Det kommer an på om dreneringen virker.

That can still mean essentially the same thing, but eller ikke emphasizes the contrast between the two possibilities.

Because eller ikke is a fixed expression meaning or not.

You should think of it as one unit:

• eller ikke = or not

So the structure is:

• om X virker eller ikke

This is the normal Norwegian way to say whether X works or not.

No. A very common alternative is:

• Det avhenger av om dreneringen virker eller ikke.

That also means It depends on whether the drainage works or not.

The difference is mainly style:

• Det kommer an på = very common, natural, everyday
• Det avhenger av = also common, slightly more formal or neutral in tone

Both are correct.

Not perfectly. A rough word-for-word breakdown is:

• om = whether / if
• dreneringen = the drainage
• virker = works
• eller ikke = or not

So the clause is:

• whether the drainage works or not

That is actually quite close to the English structure, but the full sentence should still be learned naturally as:

• Det kommer an på om dreneringen virker eller ikke.
• It depends on whether the drainage works or not.

Normally, no.

• om here means whether
• hvis means if in the sense of in case / on condition that

So:

• Det kommer an på om dreneringen virker eller ikke.
  = It depends on whether the drainage works or not.

But hvis would suggest a condition rather than an indirect question, which is not the right structure here.

A good rule:

• Use om for whether
• Use hvis for conditional if

It breaks down like this:

• Det = dummy subject
• kommer an på = depends on
• om dreneringen virker eller ikke = whether the drainage works or not

So the pattern is:

• Det kommer an på + subordinate clause

This is a very useful structure to learn, because you can reuse it with many other clauses, for example:

• Det kommer an på om han har tid. = It depends on whether he has time.
• Det kommer an på om de kan hjelpe. = It depends on whether they can help.