Learn Hardcore Indonesian: Apartemen itu ada kebocoran kecil di langit-langit kamar mandi. - That apartment has a small leak in the bathroom ceiling.

Colloquially, Indonesians often use a topic–comment pattern: Apartemen itu, ada kebocoran kecil … (with a pause/comma after itu). In careful or written Indonesian, it’s clearer to mark the location explicitly:

Di apartemen itu ada kebocoran kecil di langit-langit kamar mandi.
Ada kebocoran kecil di langit-langit kamar mandi apartemen itu. All three are understandable, but the versions with di apartemen itu or moving apartemen itu after the bathroom phrase are more standard.

What exactly does itu mean here?

Itu is the distal demonstrative “that,” and often functions like English “the” for known/previously mentioned things. Apartemen itu = “that/the apartment (we both know about).” You can swap it for:

ini = this (near speaker): apartemen ini
tersebut = the aforementioned (formal): apartemen tersebut

Why use ada? Is it “there is/are” or “have”?

Here ada is existential: “there is/are.” Indonesian often expresses “have” by stating existence in a location:

Di apartemen itu ada kebocoran kecil … = “There is a small leak in that apartment …” If you want an explicit “have,” you can use:
Apartemen itu punya kebocoran kecil … (neutral, everyday)
Apartemen itu memiliki kebocoran kecil … (more formal) But for problems/issues, ada feels most natural.

Could I say “in the roof” instead of “in the ceiling”? What’s the difference between langit-langit and atap?

Langit-langit = ceiling (inside a room).
Atap = roof (top covering of the building). In an apartment interior, use langit-langit (or plafon). Di atap kamar mandi would imply the building’s roof above the bathroom, not the interior ceiling.

Why is langit-langit written with a hyphen?

It’s reduplication. Langit means “sky”; reduplicated langit-langit means “ceiling.” Standard Indonesian uses a hyphen to mark full reduplication. You’ll also hear the loanword plafon for ceiling, very common in everyday speech: plafon kamar mandi.

Do adjectives go after nouns? Why kebocoran kecil and not kecil kebocoran?

Yes, descriptive adjectives usually follow the noun:

kebocoran kecil = small leak
kamar mandi bersih = clean bathroom Placing the adjective before the noun is generally ungrammatical in Indonesian (with a few fixed exceptions).

Do I need an article like “a”? Should I add sebuah?

Articles don’t exist in Indonesian. Ada kebocoran kecil … already means “there is a small leak.” You may add a classifier if you want to stress “one”:

Ada satu kebocoran kecil … (one small leak)
Ada sebuah kebocoran kecil … (a small leak; acceptable, but often omitted in speech)

Should it be kebocoran or bocoran? What’s the difference?

Both exist, but usage differs:

Kebocoran (ke- -an noun) is standard for physical leaks: kebocoran air/gas, kebocoran atap.
Bocoran is also used, but commonly for “leaks” of information: bocoran ujian, bocoran film. In your sentence, kebocoran kecil is the safest, most neutral choice.

Is the location phrase di langit-langit kamar mandi placed correctly?

Yes. It specifies where the leak is. You can vary word order for emphasis:

Ada kebocoran kecil di langit-langit kamar mandi (apartemen itu). (neutral)
Di langit-langit kamar mandi (apartemen itu) ada kebocoran kecil. (fronts the location) Both are natural.

Does the sentence clearly say it’s the apartment’s bathroom? How do I avoid ambiguity?

To make it explicit, anchor the bathroom to the apartment:

Ada kebocoran kecil di langit-langit kamar mandi apartemen itu. Without apartemen itu after kamar mandi, listeners will usually infer it, but the added phrase removes doubt.

How do I negate this? Is it bukan or tidak?

Use tidak ada to negate existence:

Di apartemen itu tidak ada kebocoran di langit-langit kamar mandi. Don’t use bukan here; bukan negates nouns/equatives, not existence.

How would a native politely report this problem?

A natural, polite report:

Pak/Bu, di apartemen saya ada kebocoran kecil di langit-langit kamar mandi. Bisa tolong dicek? You can add urgency or timing:
Sepertinya dari tadi malam. (Seems since last night.)

Could I use terdapat instead of ada?

Yes. Terdapat is a more formal/literary alternative:

Terdapat kebocoran kecil di langit-langit kamar mandi apartemen itu. It’s common in reports/notices; in conversation, ada is more natural.

What’s the nuance difference between kebocoran kecil and sedikit bocor?

Kebocoran kecil treats “leak” as a thing (small in size/extent).
Sedikit bocor treats “leaky” as a state (“a bit leaky”). Examples:
Ada kebocoran kecil di plafon. (There’s a small leak.)
Plafon kamar mandi sedikit bocor. (The ceiling is a bit leaky.) Both are fine; pick based on whether you want a noun or an adjectival predicate.

Could I say “the bathroom ceiling is leaking” without ada?

Yes, use bocor as the predicate:

Langit-langit kamar mandi (apartemen itu) bocor. Optionally add degree/aspect:
Sudah bocor (has started leaking/already leaking)
Masih bocor (still leaking)

Where else can I put itu to mark definiteness?

You can attach itu to different parts:

Apartemen itu ada kebocoran kecil … (that apartment)
… di langit-langit kamar mandi itu. (that bathroom)
… ada kebocoran kecil itu. (that small leak—odd unless previously identified) Usually you place itu after the specific noun you want to mark as known.

Any spelling tips? di vs di-?

di as a preposition meaning “in/at/on” is written separately: di langit-langit, di apartemen.
di- as a passive prefix is attached to the verb: diperbaiki (be repaired). Your sentence uses di as a preposition, so it must be separate.

How do I express time or completion (has/had a leak) since Indonesian has no tense?

Add time/aspect words:

Kemarin/baru saja ada kebocoran kecil … (Yesterday/just now there was a small leak …)
Sudah ada kebocoran kecil … (There has already been a small leak …)
Tadi malam ada kebocoran kecil … (Last night there was a small leak …)

Are there common synonyms for kamar mandi in this context?

Yes:

Kamar mandi = bathroom (often includes shower; may include toilet).
Toilet or WC (pronounced “weh-ceh”) = toilet/restroom.
Kamar kecil = euphemistic “restroom,” a bit formal/old-fashioned. Choose based on what you mean and your audience; kamar mandi is the safest general term.