Подставьте ведро, осмотрите трубу и сфотографируйте повреждение.

Because they are in the imperative form, and -те / -ьте is the ending used for:

• plural you (вы)
• or formal/polite singular you

So подставьте, осмотрите, and сфотографируйте all mean do X! when speaking politely or to more than one person.

Compare:

• подставь — put it underneath! (informal, to one person)
• подставьте — put it underneath! (formal or plural)

The same pattern applies to the other two verbs.

Russian usually prefers the perfective imperative when you are telling someone to perform a specific action and complete it.

Here, the speaker wants three finished results:

• put a bucket under it
• inspect the pipe
• take a photo of the damage

So the perfective forms are natural:

• подставьте
• осмотрите
• сфотографируйте

If you used imperfective imperatives, the meaning would often shift toward something like be doing this, do this as a process, or try doing this, depending on context. For clear practical instructions, perfective is very common.

Подставьте comes from подставить. In this context it means something like:

• place underneath
• put under
• hold under

So Подставьте ведро means Put a bucket underneath — for example, under a leak so water falls into it.

This verb is more specific than just поставьте (put/place). The prefix под- adds the idea of underneath.

They are in the accusative case, because each one is the direct object of a verb:

• Подставьте ведро — put the bucket underneath
• осмотрите трубу — inspect the pipe
• сфотографируйте повреждение — photograph the damage

What changes?

• ведро is neuter inanimate, so nominative and accusative are the same: ведро
• труба is feminine, so accusative singular changes from -а to -у:
  труба → трубу
• повреждение is neuter inanimate, so it stays the same in accusative: повреждение

So the only visibly changed noun here is трубу.

Because осмотреть is a transitive verb meaning inspect/examine something directly, so it normally takes a direct object in the accusative:

• осмотреть трубу — inspect the pipe
• осмотреть комнату — inspect the room

You could add a prepositional phrase if you wanted to specify what to inspect on the pipe:

• осмотрите трубу на наличие повреждений — inspect the pipe for damage
• осмотрите трубу внимательно — inspect the pipe carefully

But осмотрите трубу by itself is already complete and natural.

They are related, but not the same.

• посмотрите usually means look or have a look
• осмотрите means inspect/examine carefully

In this sentence, the idea is not just to glance at the pipe, but to check it for a problem. That is why осмотрите is the better choice.

Compare:

• Посмотрите на трубу — Look at the pipe.
• Осмотрите трубу — Inspect the pipe.

Because it is built from the verb фотографировать (to photograph / to take pictures) with the perfective prefix с-, giving сфотографировать (to photograph, to take a photo of something once / successfully).

Then the imperative polite/plural ending -йте is added:

• сфотографировать → сфотографируйте

It is long, but very common in Russian. The same idea can sometimes be expressed more colloquially with:

• сделайте фотографию повреждения — take a photograph of the damage
• сделайте фото повреждения — take a photo of the damage

But сфотографируйте повреждение is perfectly natural.

The word order is natural because it matches the likely sequence of actions:

1. Подставьте ведро
2. осмотрите трубу
3. и сфотографируйте повреждение

So the order helps present the instructions step by step.

Russian word order is flexible, and some changes are possible, but this version sounds clear and practical. For example, you could move things around for emphasis, but in instructions the straightforward order is best.

It is usually neutral and appropriately polite.

Because the verbs use -ьте, the sentence can be addressed:

• politely to one person
• or to several people

In instruction-style language, imperatives are not automatically rude. They are normal in:

• manuals
• workplace instructions
• emergency guidance
• repair advice

So this sounds like a practical instruction, not an insult or a harsh order.

You would usually use the singular informal imperative forms:

• Подставь ведро, осмотри трубу и сфотографируй повреждение.

Changes:

• подставьте → подставь
• осмотрите → осмотри
• сфотографируйте → сфотографируй

This is the ты version, used with one person informally.