Je třeba zapojit přívod vody a odpadní hadici.

Je třeba is an impersonal expression meaning it is necessary, it is needed, or one needs to.

In this sentence, it introduces a general instruction rather than saying who must do it. So the feeling is:

• It is necessary to connect ...
• You need to connect ...

It is common in manuals, instructions, and formal written Czech.

After je třeba, Czech normally uses an infinitive to say what action is necessary.

So the pattern is:

• je třeba + infinitive

Examples:

• Je třeba počkat. = It is necessary to wait.
• Je třeba zavolat technika. = It is necessary to call a technician.
• Je třeba zapojit... = It is necessary to connect...

So zapojit stays in the basic dictionary form because it is not conjugated here.

Here zapojit means something like connect, hook up, or attach properly so that it functions.

It is often used for putting something into operation by connecting it:

• electrical devices
• hoses
• appliances
• cables

In other contexts, zapojit can also mean involve or engage, but here it clearly means a physical connection.

Because hadici is the accusative singular form of hadice.

The noun hadice is feminine, and here it is a direct object of zapojit. Czech changes noun endings depending on case.

So:

• nominative: hadice
• accusative: hadici

That is why the sentence has odpadní hadici.

Because the two nouns belong to different genders and declension patterns.

• přívod is masculine inanimate
• hadice is feminine

In the accusative singular:

• masculine inanimate nouns often look the same as the nominative
• feminine nouns often change ending

So:

• přívod → přívod
• hadice → hadici

Both are objects of zapojit, but they show that role differently.

Vody is genitive singular of voda.

It depends on přívod. The phrase přívod vody literally means supply/inlet of water.

This is a very common Czech noun pattern:

• přívod vody = water supply / water inlet
• láhev vína = bottle of wine
• sklenice vody = glass of water

So vody is not a separate object of the verb. It belongs to the noun přívod.

Czech often uses a noun + genitive construction where English might use an adjective or a noun modifier.

So přívod vody literally means inlet/supply of water, and that is a very natural Czech way to say water supply or water inlet.

A form like vodní přívod could exist in some contexts, but přívod vody is the ordinary, straightforward phrasing here.

Odpadní means waste, drain, or for wastewater/drainage, depending on context.

So odpadní hadice is a drain hose or waste hose.

It comes from odpad, which is connected with waste or drainage.

Because odpadní is a different kind of adjective from adjectives like odpadný.

In this sentence, odpadní is the standard adjective meaning drain/waste-related. It behaves like a regular hard adjective, and in the feminine accusative singular its form is:

• odpadní hadici

The form odpadnou would come from a different adjective pattern and would not mean the same thing here.

So you should learn odpadní hadice as the normal phrase for drain hose.

Because Czech often uses impersonal constructions without an expressed subject.

English says:

• It is necessary to connect...

But Czech simply says:

• Je třeba zapojit...

The je means is, but there is no real subject like English it. This is normal in Czech.

Because Czech has no articles.

English distinguishes:

• a hose
• the hose

Czech does not do that with separate words. Instead, the meaning is understood from context.

So:

• odpadní hadici can mean a drain hose or the drain hose
• přívod vody can mean a water supply/inlet or the water supply/inlet

In an instruction manual, English often uses the, while Czech simply leaves it unspoken.

Yes. They are two coordinated direct objects joined by a = and.

The structure is:

• zapojit [přívod vody] a [odpadní hadici]

So the action applies to both:

• connect the water supply/inlet
• connect the drain hose

Inside the first object, vody belongs to přívod, so the full object is přívod vody.

Yes. Czech word order is more flexible than English word order.

This sentence is neutral and natural:

• Je třeba zapojit přívod vody a odpadní hadici.

But other orders are possible depending on emphasis, for example:

• Přívod vody a odpadní hadici je třeba zapojit.

That version puts more focus on the things that need to be connected.

Still, the original order sounds very natural for instructions and manuals.

Not exactly.

• Je třeba zapojit... = It is necessary to connect...
• Musíte zapojit... = You must connect...

Je třeba is more impersonal, neutral, and typical of formal instructions. Musíte speaks directly to the reader and sounds more direct.

In manuals, Czech often prefers the more impersonal style.

Yes, zapojit is a perfective verb.

That matters because the sentence is about completing a required action: the connection should be made successfully.

The imperfective partner is zapojovat, which would suggest an ongoing or repeated process rather than a single completed step.

In instructions, perfective verbs are very common because they focus on a completed result:

• zapojit = connect, get it connected
• not zapojovat = be connecting / connect repeatedly

So je třeba zapojit sounds exactly right for a one-time instruction.