"This is water from my house" or "This water is from my house" are both of the same meaning. Why is your answer correct? I have found that this occurs quite often. The simple placement of one word in my English translation (a word that does not exist in Arabic) makes the response incorrect. I find it very frustrating when I have essentially the correct response and end up being told it is incorrect. Especially, when in the very next question, where I respond in the fashion that you have deemed correct and I then get that question wrong too. Please enlighten me, I am trying to understand.
The other sentence would read in English "This (the) water is from my house" which is not the same as "This is water from my house" "This" refers to "water from my house" not "This (the) water". At some point down the road when we get more proficient in Arabic, it will make a difference.