Learn Hardcore Indonesian: Ember biru saya isi air di keran dekat wastafel. - I fill the blue bucket with water at the faucet near the sink.

The subject is saya. The fronted Ember biru is the patient (the thing affected) placed first for emphasis/topic. Indonesian allows this object-fronting pattern:

[Object] [Agent] [Bare verb] … Example: Ember biru saya isi air … = As for the blue bucket, I fill it with water …

Why is the verb the root isi instead of mengisi?

When the object is fronted (object voice), Indonesian typically uses the bare root verb:

Object voice: Ember biru saya isi air …
Regular active: Saya mengisi ember biru (dengan air) …
Passive: Ember biru diisi (air) …

Can I rewrite this in a simpler, beginner-friendly word order?

Yes: Saya mengisi ember biru dengan air di keran dekat wastafel. You can also be more explicit about the source: Saya mengisi ember biru dengan air dari keran yang dekat wastafel.

Do I need dengan before air? Why does the original omit it?

With regular active mengisi, you normally mark the content with dengan: mengisi ember dengan air.
In the object-fronting pattern with a bare verb, a “double-object” feel is allowed: Ember itu saya isi air (no dengan) is natural. So: original is fine; the SVO version should use dengan.

Should it be di keran or dari keran?

di keran = at the tap (location of the action).
dari keran = from the tap (source of the water). You can even combine: … dengan air dari keran … if you want to specify the source.

Is dekat wastafel correct without di or yang? Should it be di dekat or yang dekat?

All are acceptable, with slight style differences:

Modifier after a noun (concise): keran dekat wastafel = the tap near the sink.
With a preposition: keran di dekat wastafel (a bit more explicit).
With a relative marker: keran yang dekat wastafel (more formal/explicit). Your sentence’s di keran dekat wastafel is natural.

Is keran the same as kran? Which is correct?

Both are used. Keran is the modern standard spelling; kran is a common variant. Both are widely understood.

What’s the best word for “sink” in Indonesian? Does wastafel always work?

Wastafel usually refers to a bathroom hand-washing sink. For a kitchen sink, people often say bak cuci piring. In casual speech you’ll also hear tempat cuci tangan for a hand-washing sink. Context matters, but wastafel will be understood.

How do I express “my blue bucket”? Is ember biru saya the only way?

Options:

Neutral/polite: ember biru saya.
More intimate/compact: ember biruku (clitic -ku).
Another variant: emberku yang biru (emphasizes “the one that is blue”). All are acceptable; ember biru saya is the safest in most contexts.

Can I use aku instead of saya? And can I say kuisi?

Yes.

Informal: aku. Example: Aku mengisi ember biru … or Ember biru aku isi air …
With the subject prefix ku- (more literary/concise): Ember biru kuisi air di keran dekat wastafel.

Can I omit the agent saya? How would the sentence change?

If you drop the agent, switch to passive:

Ember biru diisi air di keran dekat wastafel. Leaving it as Ember biru isi air … without an agent is generally not grammatical in standard Indonesian.

Why not airnya? When do I add -nya?

-nya marks definiteness/possession (“the/its”). airnya would mean “the water” (a specific water already known) or “its water.” Here you’re speaking generally, so plain air is right. You might use kerannya or wastafelnya when referring to a specific known tap/sink.

How do you pronounce air, keran, and wastafel?

air = a-ir (two syllables: “ah-eer”), not like English “air.”
keran ≈ kuh-RAHN (schwa on the first vowel).
wastafel ≈ wahs-TAH-fel (three syllables).

Where can I put the location phrase di keran dekat wastafel?

Indonesian is flexible:

End: … saya isi air di keran dekat wastafel.
Front (topicalized place): Di keran dekat wastafel, ember biru saya isi air.
After the verb in SVO: Saya mengisi ember biru dengan air di keran dekat wastafel.