Se il secchio fosse più leggero, pulirei il balcone con lo stesso straccio.

Because this sentence expresses a hypothetical or unreal condition.

In Italian, when you talk about something like if X were..., I would..., the if-clause usually uses the imperfetto congiuntivo (imperfect subjunctive), and fosse is the imperfect subjunctive of essere.

So:

• Se il secchio fosse più leggero... = If the bucket were lighter...

Compare:

• Se il secchio è più leggero... = If the bucket is lighter... → real/open possibility
• Se il secchio fosse più leggero... = If the bucket were lighter... → hypothetical / contrary to fact

So fosse is chosen because the sentence is not describing a normal fact, but an imagined situation.

Pulirei is the present conditional of pulire.

Italian uses the conditional in the main clause of this kind of hypothetical sentence:

• Se + imperfect subjunctive
• conditional

So:

• Se il secchio fosse più leggero, pulirei il balcone...
• If the bucket were lighter, I would clean the balcony...

If you said pulisco, that would mean I clean / I am cleaning, which sounds factual, not hypothetical.

So the pair is:

• fosse → hypothetical condition
• pulirei → hypothetical result

It uses the standard Italian pattern for a present unreal / hypothetical condition:

• Se + congiuntivo imperfetto
• condizionale presente

In this sentence:

• Se il secchio fosse più leggero → the condition
• pulirei il balcone con lo stesso straccio → the result

This is the equivalent of English:

• If the bucket were lighter, I would clean the balcony with the same rag.

This pattern is extremely common in Italian and is worth memorizing.

Yes, that is the usual implication.

When Italian uses this hypothetical structure, it often suggests that the condition is not true at the moment, or at least that the speaker sees it as unreal.

So:

• Se il secchio fosse più leggero... strongly suggests the bucket is not lighter now, probably too heavy.

Likewise:

• ...pulirei il balcone... suggests the speaker is not actually doing that, because the condition is not met.

So the whole sentence implies something like:

• the bucket is too heavy
• because of that, the speaker would not clean the balcony in that way

No. That is a very common mistake for learners.

After se in this kind of hypothetical sentence, Italian normally does not use the conditional. It uses the subjunctive:

• correct: Se il secchio fosse più leggero, pulirei...
• incorrect: Se il secchio sarebbe più leggero, pulirei...

A simple rule to remember is:

• after se in unreal present hypotheticals → use congiuntivo imperfetto
• in the result clause → use condizionale presente

So:
se fosse ... pulirei
not
se sarebbe ... pulirei

Because leggero agrees with il secchio, and secchio is a masculine singular noun.

Agreement works like this:

• secchio → masculine singular
• therefore the adjective must also be masculine singular
• so: leggero

Compare:

• il secchio leggero → masculine singular
• la borsa leggera → feminine singular
• i secchi leggeri → masculine plural
• le borse leggere → feminine plural

Since the sentence has il secchio, the correct form is più leggero.

Because stesso follows the same article pattern as words like stadio, strano, psicologo, etc. when the noun begins with certain consonant clusters.

The noun here is straccio, which begins with str-. Masculine singular nouns beginning with s + consonant take lo, not il.

So:

• il secchio
• but lo straccio

When you add stesso, the article still matches the noun:

• lo stesso straccio = the same rag

Other examples:

• lo stesso studente
• lo stesso specchio
• lo stesso zaino

But:

• il libro → lo stesso libro? No, actually still lo stesso libro because stesso itself begins with st-, so before stesso you use lo
• la stessa casa
• i medesimi problemi / gli stessi problemi

A useful practical rule: with stesso before a masculine singular noun, you often get lo stesso.

Stesso means same.

So lo stesso straccio means the same rag / the same cloth.

It agrees in gender and number with the noun:

• lo stesso straccio → masculine singular
• la stessa spugna → feminine singular
• gli stessi stracci → masculine plural
• le stesse scarpe → feminine plural

In this sentence, stesso is an adjective modifying straccio.

Con means with.

Here it introduces the tool or means used to do the action:

• pulire il balcone con lo stesso straccio
• to clean the balcony with the same rag

This is very normal in Italian. Some similar examples:

• scrivere con una penna = to write with a pen
• tagliare con il coltello = to cut with the knife
• aprire con la chiave = to open with the key

So con is simply the preposition showing the instrument used for cleaning.

Yes. Italian word order is fairly flexible, especially with subordinate clauses.

You could also say:

• Pulirei il balcone con lo stesso straccio se il secchio fosse più leggero.

This means the same thing.

Putting the se-clause first can make the condition feel more prominent:

• Se il secchio fosse più leggero, pulirei...

Putting it second can make the result feel more prominent:

• Pulirei..., se il secchio fosse più leggero.

Both are correct.

A more real or open condition would usually use the indicative, not the subjunctive + conditional pattern.

For example:

• Se il secchio è più leggero, pulisco il balcone.
  • If the bucket is lighter, I clean / I’ll clean the balcony.

This sounds like a real possibility.

But:

• Se il secchio fosse più leggero, pulirei il balcone.
  • If the bucket were lighter, I would clean the balcony.

This sounds hypothetical, less real, or contrary to the current situation.

So the choice of verb forms changes the speaker’s attitude:

• indicative = real / possible / factual
• subjunctive + conditional = hypothetical / unreal

The comma is normal, but not always strictly required in informal writing.

When the sentence begins with the se-clause, Italian often writes a comma before the main clause:

• Se il secchio fosse più leggero, pulirei il balcone...

This helps readability.

If the main clause comes first, a comma is also common:

• Pulirei il balcone con lo stesso straccio, se il secchio fosse più leggero.

In short:

• the comma is very natural here
• it helps separate the condition from the result
• it does not change the grammar itself

Not in this sentence structure.

Here, fosse is required because it is in the se-clause of an unreal condition.

Sarebbe is the conditional of essere, and the conditional belongs in the result clause, not normally after se in standard Italian.

So:

• correct: Se il secchio fosse più leggero, pulirei...
• not standard here: Se il secchio sarebbe più leggero...

You might use sarebbe in other kinds of sentences, for example:

• Il secchio sarebbe più leggero senza acqua.
  = The bucket would be lighter without water.

So sarebbe is a real Italian form, just not the right one after se in this particular pattern.