Instalatorul etanșează conducta, iar apa nu inundă camera.

-ul is the definite article attached to the end of the noun. So:

• instalator = installer / a plumber
• instalatorul = the installer / the plumber

Romanian usually puts the at the end of the noun, not before it as English does.

Yes. In this sentence, all three are definite singular feminine nouns:

• conductă → conducta = the pipe
• apă → apa = the water
• cameră → camera = the room

A very common pattern is that feminine nouns ending in -ă change to -a when the definite article is added.

Because Romanian normally uses a postposed definite article: it is attached to the noun itself.

Compare:

• un instalator = an installer

• instalatorul = the installer

• o cameră = a room
• camera = the room

So English uses a separate word (the), but Romanian often uses a noun ending instead.

Both are present indicative, 3rd person singular.

• etanșează = he/she/it seals
• inundă = he/she/it floods

In the sentence:

• instalatorul etanșează = the installer seals
• apa nu inundă = the water does not flood

Romanian often uses the present tense much like English does for current actions or general statements.

Because Romanian -a verbs do not all conjugate the same way.

• a etanșa belongs to a pattern that adds -ez- / -ează in some forms:

  • eu etanșez
  • el/ea etanșează

• a inunda follows a simpler pattern without -ez-:

  • eu inund
  • el/ea inundă

This is something learners usually have to memorize verb by verb, though certain patterns become familiar over time.

Iar is a coordinating conjunction. It can mean and, but it often has a slight sense of contrast, shift, or whereas.

In this sentence, iar links the two clauses:

• Instalatorul etanșează conducta, iar apa nu inundă camera.

A natural English rendering might be:

• The installer seals the pipe, and the water does not flood the room.

But iar is a bit less neutral than și. It can suggest something like and meanwhile / and as a result / whereas depending on context.

Romanian usually forms negation by putting nu directly before the conjugated verb.

• inundă = floods
• nu inundă = does not flood

So:

• apa inundă camera = the water floods the room
• apa nu inundă camera = the water does not flood the room

Unlike English, Romanian does not need a helper verb like do/does here.

Because pe is not normally used for ordinary inanimate direct objects like the pipe or the room.

In Romanian, pe often marks a direct object when it is:

• a person
• animate
• a pronoun
• or especially specific in certain contexts

For example:

• Văd omul. = I see the man.
• often Îl văd pe omul acela. = I see that man.

But with inanimate nouns like conducta and camera, you normally just use them directly, with no pe.

The main special letters here are:

• ș = sh as in ship
• ă = a short neutral vowel, like the a in about

So roughly:

• etanșează ≈ eh-tan-SHEA-zuh
• inundă ≈ ee-NOON-duh

Also:

• iar is roughly yar

These vowels are important in Romanian, because changing them can change the word.

This is the normal, neutral word order: subject + verb + object in each clause.

• Instalatorul etanșează conducta
• apa nu inundă camera

Romanian does allow more flexibility than English, because verb endings and articles carry a lot of grammatical information. But the version in your sentence is the most straightforward and natural if you are simply stating the facts.