Breakdown of Nie możemy używać łazienki, chyba że naprawisz ten zawór.
nie
no / not
ten
this (m)
móc
to be able to
naprawić
to fix (perfective)
Questions & Answers about Nie możemy używać łazienki, chyba że naprawisz ten zawór.
How exactly does chyba że work in this sentence?
Chyba że translates directly to "unless" and introduces a condition. Notice that the verb after it, naprawisz (you fix), is affirmative. You don't need to add a negative word like nie after it, unless you literally mean "unless you don't fix it".
Why is "bathroom" in the genitive case (łazienki) instead of the accusative (łazienkę)?
This is because of the verb używać (to use). In Polish, the verb używać always requires the object being used to be in the genitive case, regardless of whether the sentence is positive or negative.
Why is the future tense naprawisz used here instead of a present tense verb?
In English, we say "unless you fix" using the present tense to talk about a condition in the future. Polish is strictly logical here: since the fixing has to happen in the future to solve the problem, we use the perfective future tense verb naprawisz (you will fix / you will have fixed).
Why does ten zawór (this valve) look like it's in the nominative (dictionary) case when it's the object of the verb?
Zawór is a masculine inanimate noun. For masculine inanimate nouns, the accusative case (which we use for direct objects) looks exactly the same as the nominative case. So, ten zawór is indeed in the accusative case here, it just doesn't change its spelling.