Why is "from where" instead of "from which" here? Can you help me with that?

"After the water has passed through the turbines, it continues its journey through a pipe called tailrace, from where it is then released back into the river on the opposite side of the dam"

I guess it should be "from which" in a non-restrictive attributive clause

Question

Why is "from where" instead of "from which" here? Can you help me with that?

"After the water has passed through the turbines, it continues its journey through a pipe called tailrace, from where it is then released back into the river on the opposite side of the dam"

I guess it should be "from which" in a non-restrictive attributive clause

Answer

Because it's just the place where it comes from - it's not distinguishing between different pipes.

It answers the question: Where is the water released back into the river from?

Not: Which pipe does it come from.

Answer

I feel that "from where" is slightly incorrect and that "from which" is better. But it depends on whether a pipe feels like a "thing" or a "place." If it's a thing, we would say "which," if it's a place, we would say "where."

We could complicate the question further by asking if we could say "from whence!"

Answer

"From which" is completely correct and is the superior choice.

An explicit choice is not required in order to use "which".

Other examples:
"That is a book from which I have learned a lot."
"That is a city in which many crimes occur."  ("where" can also be used)

Answer

I agree with you actually. But I don't think "from where" is incorrect. I think both are acceptable, but I slightly prefer "from which".

Answer

"From where" is the correct choice and not "from which" because it is talking about a place here. Which is used to either distinguish between two things or as a pronoun. Neither are applicable here.