Learn Hardcore Swahili: Maji ya bomba yakianza kuwa machafu, tumia chujio kusafisha. - When the tap water starts to be dirty, use a filter to clean it.

Because maji belongs to noun class 6 and takes the associative connector ya for “of.” So maji ya bomba = “water of the tap/pipe.” The connector la is used with class 5 singular nouns, not with class 6. Here the agreement follows maji, not bomba.

What exactly is yakianza?

It’s the verb with class/tense marking:

ya- = subject prefix for class 6 (agreeing with maji)
-ki- = subordinator meaning “when/if/while”
-anza = verb root “start” So yakianza ≈ “when it (they, the waters) start.”

Could I use yanapoanza instead of yakianza? What’s the difference?

Yes: Maji ya bomba yanapoanza kuwa machafu… is fine. Nuance:

-ki- = when/if/whenever; often a general condition or repeated scenario.
-napo- = “at the time/place when”; a bit more specific/anchored in time.

Why does the sentence use plural agreement (ya-, yan-, machafu) for maji when English says “water is …”?

In Swahili, maji is a plural mass noun (class 6). It triggers plural agreement:

Subject prefix: ya- (e.g., maji yamechemka)
Adjective agreement: machafu (not chafu)

Why is it kuwa machafu instead of using a single verb like kuchafuka?

Both are correct:

kuwa machafu = “to become/be dirty” (copula + adjective)
kuchafuka = “to get dirty/soil (intransitive)” You could say: Maji ya bomba yakianza kuchafuka, tumia chujio…

Is the comma necessary, and can I change the clause order?

The comma helps readability but isn’t strictly required. You can also say:

Tumia chujio kusafisha maji ya bomba yakianza kuwa machafu. Fronting the “when”-clause first is very natural in Swahili, just like in English.

What form is tumia? How do I address multiple people or be more polite?

tumia is the singular imperative “use.” Variations:

Plural imperative: tumieni
Polite: add tafadhali (e.g., Tafadhali tumia/tumieni…)
Soft advice: Unapaswa kutumia… / Mnapaswa kutumia… (“You should use …”)

What does chujio mean, and is kichujio also correct?

Both are used for “filter/strainer.” Usage varies by region and context:

chujio (often class 5/6; plural machujio) — common for strainers/filters
kichujio (class 7/8; plural vichujio) — very common for device-type filters (e.g., water filters) Either works here.

Why is it machafu and not chafu?

Adjectives agree with the noun class. For class 6 (maji), the adjective -chafu takes the class 6 prefix, yielding machafu. So maji machafu = “dirty water.”

Should it be kusafisha or kuchuja after tumia chujio?

Both work, with a nuance:

kuchuja = “to filter” (the action the filter does)
kusafisha = “to clean” (the goal/result) So you can say: Tumia chujio kuchuja/kusafisha (maji).

Can I include the object “water” explicitly in the second part?

Yes:

Noun object: Tumia chujio kusafisha maji.
Object marker: Tumia chujio kuyasafisha. Here kuyasafisha = ku- (inf.) + ya (obj. marker for class 6) + safisha.

Is the meaning conditional (“if”) or temporal (“when”) with -ki-?

-ki- can be either, depending on context. Here it’s essentially habitual/conditional: “when/if the tap water starts getting dirty…” It often implies “whenever” or a general condition.

Are there other natural ways to phrase the first clause?

Yes:

Kama maji ya bomba yanaanza kuwa machafu… (if)
Ikiwa maji ya bomba yanaanza kuwa machafu… (if, slightly formal)
Maji ya bomba yakichafuka… (when/if they get dirty)

What does bomba cover—tap or pipe?

bomba can mean tap, pipe, or hose depending on context. The fixed phrase maji ya bomba means “tap water” (water supplied through the municipal system).