Learn Hardcore Swahili: Tunaweka maji safi kwenye tanki nyuma ya nyumba. - We put clean water into the tank behind the house.

Past (we put / we put in the past):
Tuliweka maji safi kwenye tanki nyuma ya nyumba.
- tu- (we) + -li- (past) + -weka (put)
Future (we will put):
Tutaweka maji safi kwenye tanki nyuma ya nyumba.
- tu- (we) + -ta- (future) + -weka (put)

Everything else in the sentence stays the same.

Why is safi placed after maji, not before it like in English “clean water”?

In Swahili, adjectives normally come after the noun they describe:

maji safi – clean water
nyumba kubwa – big house
mtoto mdogo – small child

So maji safi is the regular and expected order: noun + adjective.

Does safi have to change to agree with maji? Should it be something like maji masafi?

No, safi stays safi for all nouns; it doesn’t take agreement prefixes.

mtu safi – a clean / decent person
watu safi – clean / decent people
maji safi – clean water

Many adjectives in Swahili do change to agree with the noun class (e.g. -chafu: maji machafu “dirty water”), but safi is one of the common invariable adjectives. So maji safi is correct and natural.

Why is there no word for “the” in “the tank” or “the house”?

Swahili does not use articles (“a”, “an”, “the”). Nouns stand on their own, and context tells you whether it means “a” or “the”:

tanki can mean a tank or the tank
nyumba can mean a house or the house

So Tunaweka maji safi kwenye tanki nyuma ya nyumba can be translated depending on context as:

We put clean water in *a tank behind a house*, or
We put clean water in *the tank behind the house.*

English must choose an article; Swahili doesn’t.

What exactly does kwenye mean, and can I replace it with katika or ndani ya here?

Kwenye is a very common preposition meaning “in / at / on” (location). In your sentence:

kwenye tanki ≈ in the tank / at the tank

You can often replace kwenye with:

katika – more formal, usually also means “in”
- Tunaweka maji safi katika tanki nyuma ya nyumba.
ndani ya – “inside (of)”
- Tunaweka maji safi ndani ya tanki nyuma ya nyumba.
- This emphasizes inside the tank.

All three are grammatically possible, but:

kwenye = neutral, very common in speech
katika = slightly more formal/written
ndani ya = specifically inside

Why is it just kwenye tanki and not something like kwenye tanki la maji (“water tank”)?

This sentence doesn’t need to say “water tank” explicitly, because it already says we are putting water there; context makes it obvious.

If you wanted to specify “water tank”, you could say:

Tunaweka maji safi kwenye tanki la maji nyuma ya nyumba.
- tanki la maji = water tank (literally: tank of water)

Both versions are fine:

kwenye tanki – in the tank
kwenye tanki la maji – in the water tank (more specific)

How does nyuma ya nyumba work? Why is there a ya in the middle?

Nyuma by itself means “back / behind”. To say “behind X”, Swahili often uses a structure like:

nyuma ya [something] – the back/behind of [something]

So:

nyuma ya nyumba = the back/behind of the house → behind the house

Similar patterns:

mbele ya nyumba – in front of the house
juu ya meza – on top of the table
chini ya kitanda – under the bed

The word ya here is a kind of “of” connector: the back *of the house*.

Why is it nyuma ya nyumba and not nyuma la nyumba? How do I know which connector to use?

The connector (ya / la / wa / cha / vya, etc.) must agree with the noun class of the first noun, which here is nyuma.

nyuma belongs to noun class 9/10, whose connector is ya.
→ nyuma ya nyumba (correct)

If the first noun were class 5 instead, you’d use la:

tanki la maji – tank of water
- tanki is class 5, connector la

So in nyuma ya nyumba, ya agrees with nyuma, not with nyumba.

Where is the object “water” in this sentence, and is the word order normal for Swahili?

The basic structure is:

Tunaweka – we put
maji safi – clean water (direct object)
kwenye tanki – in the tank (prepositional phrase)
nyuma ya nyumba – behind the house (prepositional phrase)

So the order is essentially:

Subject–Verb–Object–(place phrases)
We – put – water – in the tank – behind the house

This is very normal Swahili word order: S–V–O, then additional location details.

Can I leave out safi and just say “We put water in the tank behind the house”?

Yes. You can simply say:

Tunaweka maji kwenye tanki nyuma ya nyumba.

That means “We put water in the tank behind the house.”
Adding safi just emphasizes that the water is clean. Both versions are completely natural.

How do you pronounce nyuma and nyumba? Is ny one sound or two?

In Swahili:

ny is usually pronounced as one sound, like the “ny” in English “canyon”, or the Spanish ñ in “niño”.

So:

nyuma ≈ “nyu-ma” (nyoo-ma)
nyumba ≈ “nyu-mba” (nyoo-mba)

Try not to separate n and y like “ni-yu”; it should feel like a single consonant sound.

Is tanki a Swahili word or borrowed from English? What is its plural?

Tanki is a loanword from English “tank” (usually for water/oil tanks).

In Swahili it behaves like a class 5/6 noun:

singular: tanki – a tank
plural: matanki – tanks

Examples:

Tanki moja iko nyuma ya nyumba. – There is one tank behind the house.
Matanki mawili yako nyuma ya nyumba. – Two tanks are behind the house.

How would I say “We are putting clean water in the tank behind our house”?

You just add a possessive for “our house”:

Tunaweka maji safi kwenye tanki nyuma ya nyumba yetu.
- nyumba yetu = our house

Or a bit more literally:

Tunaweka maji safi kwenye tanki nyuma ya nyumba yetu.
(We are putting clean water in the tank behind our house.)

Everything else stays the same; you only add yetu (our).