jìrán shuǐlóngtóu lòushuǐ le, jiù mǎshàng guān zǒngfá.

既然 means something like since, now that, or given that.

In this sentence, it introduces a fact that is already accepted:

• 既然水龙头漏水了，...
• Since the faucet is leaking, ...

Compared with 因为:

• 因为 simply gives a reason: because
• 既然 often means since this is already true / since we already know this, the next step should follow naturally

So 既然 often sounds more like:

• Given that this is the case, then...
• Since that’s so, ...

That is why it often appears with 就 in the next clause.

This is a very common pattern:

• 既然 ... ，就 ...

It means:

• Since ... , then ...
• Now that ... , (we should / you should / naturally we) ...

In this sentence:

• 既然水龙头漏水了，就马上关总阀。

The 就 marks the logical result, reaction, or next step.

It does not mean then in a time-sequence sense only; here it means more like:

• in that case
• then naturally
• so

Without 就, the sentence could still be understood, but 既然 ... 就 ... is the standard and very natural pairing.

The 了 here marks a new situation or changed state.

• 漏水 = to leak
• 漏水了 = is leaking now / has started leaking / the leaking situation has occurred

This does not necessarily mean a completed action. It is not like English leaked in a simple past sense.

Here, 了 tells us that the leaking has become a real, current situation, and that is what triggers the action in the second half.

So:

• 水龙头漏水 = the faucet leaks / is leaking
• 水龙头漏水了 = the faucet has started leaking / is leaking now

In everyday speech, 了 is very common when someone notices a problem and reacts to it.

It is best to learn 漏水 here as a set expression meaning:

• to leak water
• to be leaking

So:

• 水龙头漏水 = the faucet is leaking
• 屋顶漏水 = the roof is leaking
• 管子漏水 = the pipe is leaking

Even though it is made of:

• 漏 = leak
• 水 = water

in real usage, 漏水 often functions like a verb phrase meaning to have a water leak.

Mandarin often omits the subject when it is obvious from context.

Here, the sentence sounds like:

• advice
• an instruction
• a command
• a practical response

So the understood subject is something like:

• you
• we
• someone present

In fuller form, it could be:

• 既然水龙头漏水了，你就马上关总阀。
• Since the faucet is leaking, you should immediately turn off the main valve.

But in natural Chinese, leaving out 你 is very common when giving instructions.

It can feel like a practical instruction or strong suggestion.

Because there is no explicit subject, and because of 就马上关总阀, it sounds like:

• then immediately turn off the main valve
• you should immediately turn off the main valve

So in English terms, it is somewhere between:

• an imperative
• advice
• a logical recommendation

Mandarin often leaves this kind of force to context rather than marking it very directly.

总阀 means the main valve.

• 总 = main / overall / general
• 阀 = valve

In this context, it means the main water shutoff valve for the system, house, or apartment.

So:

• 关总阀 = turn off the main valve

This is different from just turning the faucet handle itself. The sentence suggests a stronger emergency action, probably because there is a leak problem.

In Mandarin, time words and adverbs such as 马上 usually come before the main verb.

So the natural order is:

• 马上关总阀
• immediately turn off the main valve

Structure:

• 马上 = adverb
• 关 = verb
• 总阀 = object

So:

• 就马上关总阀 = then immediately turn off the main valve

Putting 马上 after the verb would sound unnatural here.

Yes. All of these can work, though the feeling is a little different.

• 马上 = immediately / right away
• 立刻 = immediately, slightly more direct or formal
• 赶快 = hurry up and..., often more conversational and urgent

Examples:

• 既然水龙头漏水了，就马上关总阀。
• 既然水龙头漏水了，就立刻关总阀。
• 既然水龙头漏水了，就赶快关总阀。

All are natural. 马上 is very common and neutral.

All of these are possible, but they are slightly different in style.

1. 关总阀

   • simple and direct
   • common in instructions

2. 关掉总阀

   • emphasizes shutting it off completely
   • very natural in speech

3. 把总阀关上

   • uses the 把 construction
   • focuses on what is being handled and brought to a result
   • also very natural

So these are all possible:

• 既然水龙头漏水了，就马上关总阀。
• 既然水龙头漏水了，就马上关掉总阀。
• 既然水龙头漏水了，就马上把总阀关上。

The original version is concise and instruction-like.

Yes, it helps show the two-part structure clearly:

• 既然水龙头漏水了，
• 就马上关总阀。

The comma separates:

1. the known reason or situation
2. the response or conclusion

In writing, this is very natural with 既然 ... ，就 ...

In speech, there is usually a small pause there too.

Yes, sometimes, but 既然 ... 就 ... is the most common and expected pattern.

For example, people may say:

• 既然你知道，为什么不说？
• Since you knew, why didn’t you say anything?

Here there is no 就, because the second clause is a question, not a straightforward result clause.

But in a sentence like the one here, where the second part is the natural action to take, 就 is the most normal choice.

It is not overly formal, but it is a bit more structured than very casual speech.

It is common in:

• conversation
• advice
• explanation
• argument
• practical instructions

Native speakers also often use similar patterns like:

• 都已经...了，那就...
• 既然这样，那就...

So 既然 is perfectly natural, but it does have a slightly logical, reasoning-based feel.

That literal translation is understandable, but it sounds unnatural in English.

The better English is something like:

• Since the faucet is leaking, immediately turn off the main valve.
• Now that the faucet is leaking, turn off the main valve right away.

This is because:

• 漏水了 is about a current problem or new situation, not just a finished past event
• 关 with a valve is usually translated as turn off rather than close in everyday English, though close the valve is also possible technically

So a more natural English understanding is:

• The faucet is leaking, so shut off the main valve immediately.