Der er noget galt med røret under vasken.

In this sentence, der is an expletive or dummy subject, similar to English there in There is something wrong...

So:

• Der er... = There is/There are...

Here, der does not mean there as a place. It is just used to introduce the existence of something.

Compare:

• Der er noget galt. = There is something wrong.
• Bogen er der. = The book is there.

In the second sentence, der really does mean a location.

Actually, er is the verb, and Danish normally puts the verb in second position in main clauses.

So the structure is:

• Der = dummy subject
• er = verb
• noget galt... = the rest of the sentence

This is very normal Danish word order:

• Der er en bog på bordet. = There is a book on the table.
• Der ligger en kat i stolen. = There is a cat in the chair.

So Der er noget galt... is the standard and natural pattern.

Noget means something.

So:

• noget = something
• ingenting / ikke noget = nothing

In this sentence, noget galt literally means something wrong.

Examples:

• Der er noget i vejen. = Something is wrong.
• Jeg har noget til dig. = I have something for you.

Galt means wrong in this expression.

It comes from the adjective gal, which can mean wrong, mad/crazy, or mistaken, depending on context.

Why galt? Because Danish adjectives often take a -t form in certain situations, including after noget in expressions like this.

So:

• gal = base form
• galt = neuter/common adverb-like form used here

Very common expression:

• Der er noget galt. = There is something wrong.

You should learn noget galt as a fixed, natural phrase.

Yes, very much so.

Der er noget galt is an extremely common Danish expression meaning:

• Something is wrong
• There is something wrong

Other similar expressions are:

• Der er ikke noget galt. = There is nothing wrong.
• Hvad er der galt? = What is wrong?
• Er der noget galt med bilen? = Is there something wrong with the car?

So it is useful to learn the whole pattern:

• Der er noget galt med ...

The preposition med means with.

So:

• noget galt med røret = something wrong with the pipe

This is also a common pattern in both Danish and English:

• Der er noget galt med computeren. = There is something wrong with the computer.
• Hvad er der galt med ham? = What is wrong with him?

So med is the normal preposition after noget galt when you say what the problem concerns.

Røret means the pipe.

The noun is:

• et rør = a pipe
• røret = the pipe

Danish usually adds the definite article to the end of the noun instead of using a separate word like English the.

So:

• et rør = a pipe
• røret = the pipe

You would not say en rør, because rør is a neuter noun, so its indefinite article is et, not en.

Unfortunately, grammatical gender in Danish often has to be learned together with the noun.

So it is best to memorize nouns with their article:

• et rør
• en vask
• et bord
• en stol

Then you can form the definite version correctly:

• et rør → røret
• en vask → vasken

There is no perfect rule that lets you always predict whether a noun takes en or et, so learning the article with the word is very important.

Under means under/below, and vasken means the sink.

So:

• under vasken = under the sink

The noun is:

• en vask = a sink
• vasken = the sink

Again, Danish puts the definite article at the end:

• en vask
• vasken

Because the sentence is talking about a specific pipe and a specific sink, not just any pipe or any sink.

• røret = the pipe
• vasken = the sink

This sounds natural if the speaker means the pipe located under that sink, for example in a house or apartment.

If you changed them to indefinite forms, the meaning would become less specific:

• Der er noget galt med et rør under en vask.

That sounds more like There is something wrong with a pipe under a sink, which is much less natural in this context.

In practice, under vasken is understood as describing røret:

• the pipe under the sink

So the meaning is:

• There is something wrong with the pipe [that is] under the sink.

It does not usually mean that something wrong is physically located under the sink. The most natural reading is that the pipe under the sink is the thing with the problem.

The structure is:

• Der = dummy subject
• er = is
• noget galt = something wrong
• med røret = with the pipe
• under vasken = under the sink

So you can think of it as:

• There is
  • something wrong
    • with the pipe
      • under the sink

This is a very useful model for making your own sentences:

• Der er noget galt med bilen.
• Der er noget galt med døren.
• Der er noget galt med lyset i køkkenet.

In Danish, yes/no questions are usually formed by putting the verb before the subject.

So:

• Der er noget galt med røret under vasken.
  becomes
• Er der noget galt med røret under vasken?

That means:

• Is there something wrong with the pipe under the sink?

This is a very common pattern:

• Er der en læge her? = Is there a doctor here?
• Er der problemer? = Are there problems?

Røret can be tricky for English speakers because of ø.

A rough guide:

• rør has a vowel sound that does not exist exactly in English
• -et is usually a light ending, often like a weak uhd/ed sound depending on accent and speech speed

Important points:

• ø is a rounded front vowel; you shape your lips somewhat as for o, but place your tongue more like for e
• the Danish r also affects the vowel quality

You do not need perfect pronunciation immediately, but it helps to listen carefully to native audio and repeat whole chunks such as:

• røret
• under vasken
• der er noget galt

Yes. That is another very common and natural way to say it.

• Der er noget galt med røret under vasken.
• Der er noget i vejen med røret under vasken.

Both mean that something is wrong with the pipe under the sink.

A small nuance:

• noget galt = very direct, common
• noget i vejen = also very common, sometimes slightly softer or more idiomatic

Both are useful expressions to learn.