[susan53]

Grammatically the use of the since clause (denoting past to present time) and then a simple present verb doesn't follow logically. I don't know what Water Homes is - a TV programme perhaps (as you say "episode")? Was the presenter speaking spontaneously? Always explain the context. If so , then yes - illogicalities are going to slip in. It's not a matter of being "correct" or not - s/he has said one thing, then goes on to something else "forgetting" what came before and, as you said, emphasising the idea that was at the forefront of his/her mind. In fact it happens twice in this sentence - it's also illogical grammatically because the unstated subject of a non-finite verb in a subordinate clause (here completing) should be the same as the subject in the main clause. But here it's not. It's not the "fruits of their labour" which completed the pool but, presumably, the people who live in the house. This is known as a "dangling participle" - google it.


So the sentence is illogical grammatically from two points of view. But this is normal in spoken language. You can't equate spontaneous spoken language with written language. They are produced under completely different conditions - spoken language is produced in "real time" (the speaker has to decide what s/he wants to say and how to say it "on the spot") and can't be proof read or changed to make ideas clearer. As I write this, I'm constantly going back to correct errors or to erase, add or rephrase. Even after posting the answer, I've used the "edit" button about four times so far. But that's not possible in spoken language. So the features will be different. This particular feature - where the end of a sentence doesn't follow on grammatically from the beginning- is called anacoluthon. Again, google it for more information. It is sometimes used deliberately in writing as a literary or rhetorical device, but is very, very common in spoken language for the reasons I've suggested. And because listening also happens in "real time", most of the time we don't even notice. It's clear what the speaker wants to say, and we just follow the line of thought.