Breakdown of Вода проходит через трубу, а потом через фильтр.
вода
water
а
and (contrastive)
потом
then
проходить
to pass
Questions & Answers about Вода проходит через трубу, а потом через фильтр.
Why do we use the accusative case after через?
The preposition через (meaning "through" or "across") always requires the accusative case. It implies motion crossing a boundary, space, or medium, like the water moving through the pipe (трубу) and the filter (фильтр).
Why does the ending change for трубу but not for фильтр?
Both words are in the accusative case because of через. However, труба is a feminine noun, so its ending changes from -а to -у (трубу). Фильтр is a masculine inanimate noun, and masculine inanimate nouns do not change their endings in the accusative case, so it looks exactly the same as its dictionary form.
The English translation says "and then", so why is the Russian word а used instead of и?
While и simply links two similar things together, а is often used to show a sequence of events or a slight shift in focus. When paired with потом (then), а потом is a very natural and common way to say "and then" or "and next" in Russian, separating the first step (the pipe) from the next step (the filter).
Why is the verb проходит used here instead of just идёт?