Die watertenk is agter die stoombeheerknop.

Because Afrikaans uses die as the definite article, meaning the.

In this sentence, there are two separate nouns:

• die watertenk
• die stoombeheerknop

Each one needs its own definite article, just like in English:

• the water tank
• the steam control knob

So Afrikaans repeats die in the same way English repeats the.

No. One very learner-friendly feature of Afrikaans is that die does not change for grammatical gender.

Afrikaans does not use separate masculine, feminine, and neuter definite articles the way some other Germanic languages do. For singular definite nouns, die is used across the board.

So:

• die watertenk
• die knop
• die tafel

all use the same article.

Agter is a preposition meaning behind or at the back of, depending on context.

Here it tells you the location of the water tank in relation to the steam control knob.

So the structure is:

• Die watertenk = the subject
• is = is
• agter die stoombeheerknop = behind the steam control knob

It works very similarly to English prepositions of place.

This is the normal basic Afrikaans word order for a simple statement:

Subject + verb + rest of sentence

So here:

• Die watertenk = subject
• is = verb
• agter die stoombeheerknop = prepositional phrase showing location

That is very similar to English:

• The water tank is behind the steam control knob.

Afrikaans word order often feels familiar to English speakers in straightforward main clauses like this.

Yes. Is is the Afrikaans present-tense form of the verb to be in this kind of sentence.

In Afrikaans, is is used very widely and does not change as much as English verbs do.

For example:

• Die tenk is groot. = The tank is big.
• Die knop is warm. = The knob is warm.

So in your sentence, is simply links the subject to its location.

Because Afrikaans, like Dutch and German, very often forms compound nouns by joining words together.

So:

• stoom = steam
• beheer = control
• knop = knob

Together they form one compound noun:

• stoombeheerknop = steam control knob

This is completely normal in Afrikaans. English sometimes writes similar ideas as separate words, but Afrikaans often prefers one combined word.

A useful strategy is to read Afrikaans compounds from right to left.

The last part is usually the main thing, and the earlier part(s) describe it.

So:

• watertenk = a tank for water
• stoombeheerknop = a knob for steam control

This helps a lot with long Afrikaans nouns. If you identify the last element first, the meaning usually becomes much easier to unpack.

A rough English-friendly guide would be:

• watertenk ≈ VAH-ter-tenk
• stoombeheerknop ≈ STOHM-buh-KHEER-knop
• agter ≈ AKH-ter

A few pronunciation notes:

• w in Afrikaans is usually closer to English v
• g in agter is a harsher throat sound, not an English g
• oo in stoom is a long vowel, roughly like o in more, though not exactly the same
• knop starts with a pronounced k, unlike English knob

Pronunciation varies somewhat by speaker and accent, but those approximations will point you in the right direction.

Yes. In many contexts, agter covers the same basic idea as English behind.

Depending on the situation, English might translate it as:

• behind
• at the back of
• sometimes even in back of

The exact English wording depends on what sounds most natural in context, but the Afrikaans preposition itself is straightforwardly agter.

Normally, no. If you mean the steam control knob, then die is needed before stoombeheerknop.

So:

• agter die stoombeheerknop = behind the steam control knob

If you removed it, the phrase would no longer mean exactly the same thing and would usually sound incomplete or unnatural in standard Afrikaans.

Typically:

• watertenk → watertenks
• stoombeheerknop → stoombeheerknoppe

Afrikaans plurals are not completely predictable from one rule alone, but common endings include:

• -e
• -s
• sometimes other changes depending on the word

So it is best to learn plural forms along with the noun when possible.

It is neutral and completely normal standard Afrikaans.

There is nothing especially formal, old-fashioned, or slangy about it. It sounds like the kind of sentence you might find:

• in instructions
• in a product manual
• in a description of a machine or appliance

So it is a very useful pattern for practical, everyday written Afrikaans.