My Kenyan Swahili tutor is unfazed by these matters; for him it is sufficient that "mfereji" is something that brings water, a canal, a pipe, or a tap and the context will give you the specific intended meaning.
I notice that the Suez Canal is an mfereji in Swahili. And to give someone a tap on the shoulder you don't have to be a plumber.!
My real problem is that I am 75 and my memory is too poor to learn such a different language.
I came to complain about this too. I speak Swahili and am just taking the course to refresh on some basic words that I've lost over the years living in the West and some of these words on duolingo are either wrong or when you type in the write word, they mark you wrong. For instance, I typed pocket for mfuko and it was wrong.