suidou ha tukaeru noni, gasu ga mada tukaenai node ryouri ga dekimasen.

This is a very common question.

In this sentence, 水道は sets up the topic: as for the water service / water supply. It gives the background for what the speaker is talking about.

Then ガスが introduces the thing that is specifically in the condition 使えない: the gas is not usable yet.

So the sentence has a contrast like this:

As for the water, it can be used, but the gas still cannot be used...

Using は with 水道 helps create that contrast. The が with ガス sounds more like identifying the thing that is not available.

You could think of it as:

• 水道は = speaking of water service
• ガスが = it is the gas that is still unusable

水道 usually means water supply, running water, or water service. In everyday situations like moving into a new apartment, it often refers to the utility service, not just the physical faucet.

So here it does not mean only a tap. It means something like:

the water is on / water service is available

That is why 使える makes sense with it.

Yes, 使える is the potential form of 使う, so its basic meaning is can use.

But in sentences about utilities, machines, apps, rooms, etc., 使える often means:

• is usable
• is available
• works
• is ready to use

So here:

• 水道は使える = the water is usable / the water is on
• ガスがまだ使えない = the gas is still not available / the gas is not on yet

It is not only about the speaker’s ability. It is about whether the thing itself is available for use.

使う is a u-verb. To make the potential form, change the final う sound to the corresponding え sound and add る:

• 使う
• 使える

So:

• 使う = to use
• 使える = can use / is usable

The negative form is:

• 使えない = cannot use / is not usable

And the polite negative used in the sentence is:

• できません from できる

Here のに means although, even though, or despite the fact that.

It shows contrast or an unexpected situation:

水道は使えるのに、ガスがまだ使えない = Even though the water works, the gas still doesn’t work

The idea is that the first fact might make you expect things to be okay, but the second fact goes against that expectation.

So のに is stronger than just a plain and. It adds a feeling of contrast.

They do different jobs.

のに connects two ideas with contrast:

• 水道は使えるのに、ガスがまだ使えない
• The water works, but the gas still doesn’t

ので gives a reason/cause:

• ガスがまだ使えないので料理ができません
• Because the gas still can’t be used, I can’t cook

So the structure is:

1. Fact A contrasts with Fact B
2. Fact B causes Result C

In short:

• のに = although / even though
• ので = because / so

Yes, it could.

You could say: ガスがまだ使えないから、料理ができません。

That would also mean Because the gas still can’t be used, I can’t cook.

The difference is nuance:

• ので sounds a bit softer, more explanatory, and often a little more formal
• から sounds more direct and conversational

Both are very natural. In this sentence, ので fits well because the speaker is calmly explaining the reason.

まだ with a negative often means not yet.

So:

• まだ使えない = cannot use it yet

This is a very common pattern in Japanese:

• まだです = not yet
• まだ食べていません = haven’t eaten yet
• まだ終わっていません = it hasn’t finished yet

Without まだ, 使えない would simply mean cannot use. Adding まだ suggests the situation may change later.

This is one of the most important grammar points here.

The verb できる usually does not take を for the thing that is possible. Instead, that thing is often marked by が.

So:

• 料理ができる = can cook / cooking is possible
• 日本語が話せる = can speak Japanese
• ピアノができる = can play piano / is good at piano, depending on context

In Japanese, できる often works more like is possible than like a normal transitive verb.

So 料理ができません is the natural form.

Yes, that is a very good way to understand it.

A very literal breakdown is:

• 料理 = cooking / meal preparation
• ができません = is not possible / cannot be done

So the sentence sounds like: Because the gas still can’t be used, cooking is not possible.

In natural English, we usually translate that as: I can’t cook.

Japanese often avoids explicitly saying I when it is obvious from context.

Because Japanese often omits subjects when they are understood from context.

In this sentence, it is obvious that the speaker means something like:

• I can’t cook
• We can’t cook

Japanese does not need to say 私は unless there is a reason to emphasize it or contrast it with someone else.

So the sentence sounds natural without a pronoun.

It can in some contexts, but not here.

By itself, 料理ができません could sometimes be understood as:

• I can’t cook
• I’m not able to cook
• possibly I’m not good at cooking, depending on context

But in this sentence, the reason is clearly given:

ガスがまだ使えないので = because the gas still cannot be used

So here it definitely means: I can’t cook because it’s not possible right now, not I lack cooking skill.

できません is the polite negative form of できる.

Compare:

• できない = plain form
• できません = polite form

The sentence uses polite style overall:

• 使えない is plain because it comes before ので
• できません is sentence-final, so it shows the overall politeness level

This is very common in Japanese. A clause before ので, から, けど, のに, etc. can be plain, while the final verb is polite.

It is not considered unnatural here.

In Japanese, subordinate clauses often use plain forms even in polite speech. The politeness is usually shown most clearly at the end of the sentence.

So this pattern is normal:

• ガスがまだ使えないので、料理ができません。

The first clause is plain because it is not the final main statement. The final verb できません sets the polite tone of the whole sentence.

Yes, ガスはまだ使えない is also possible, but the nuance changes a little.

• ガスがまだ使えない focuses on the fact that the gas is the thing that is still unusable.
• ガスはまだ使えない would make the contrast even stronger: as for the gas, it still can’t be used

Since the sentence already has 水道は, choosing ガスが keeps the second part from sounding too heavy with contrast markers. It sounds natural and balanced.

A helpful breakdown is:

水道 は 使える のに、 As for the water, it works / can be used, although...

ガス が まだ 使えない ので because the gas still cannot be used

料理 が できません。 cooking is not possible / I can’t cook

So the logic is:

Even though the water works, because the gas still doesn’t work, I can’t cook.

It may feel slightly repetitive in English because Japanese is comfortable stacking a contrast clause and a reason clause in one sentence.