It’s true. Check out this video starting at 4:08.
(Mark Rober - science channel)
I sorta didn’t want to know this.
I’m not clicking that link as I feel it’s probably youtube clickbaity, but is it comparable to adding ammonia to bleach?
I learned this from a friend that runs a pool supply business. He explained what chemical reactions were going on but I can’t remember the details.
When I was a grad student, there was an indoor pool in a basement that reeked of chlorine. I guarantee you that grad students were not peeing in the pool en masse. Chlorine does have an odor on it own.
Chlorine in an unused pool definitely has an odor. Not the same as chlorine+urine, but it does.
(Former maintainer of two home pools.)
It is not, I noted that is Mark Rober’s science channel. He is a former NASA & Apple engineer.
I definitely didn’t want to know this. 
Damn, I just gargled while swimming.
No pee in my hot tub but I can definitely smell the chlorine if I put in too much.
Teeth whitening, again?
Interesting. In the video, Mark put in 4x the recommended amount of chlorine and was unable to smell it.
I came here to say this. My recollection of indoor pools is that they always have a faint but unmistakably odor of chlorine. And it’s not because anyone is peeing in them – it’s exactly the odor of bleach. You also get some sense of bleach smell when you’ve been in any pool, indoor or outdoor, if it’s chlorinated.
That’s why some pool owners prefer a salt sanitation method, which produces chlorine compounds from salt, rather than adding chlorine directly. A friend has such a pool and I’ve never noticed even a hint of chlorine, even though technically such pools are not chlorine-free.
Then Mark has a shitty sense of smell. I can smell the chlorine in tap water when they add a lot.
I did use a friend’s pool a while ago that had less chlorine than most pools, because it’s only used by adults who don’t pee in it, and it’s not used very much. And it smelled MUCH less unpleasant than the typical pool. I even asked about it. But I could tell it there was chlorine it in.
My first thought too.
An additional data point- I worked maintenance in a facility with a pool when I was in high school, and we drained and retiled the pool during my time there; if anything, the freshly-refilled pool had a stronger chlorine smell than it normally did.
My understanding is that the smell is the product of various organic molecules interacting with chlorine. With that being true, you might get it from bacteria, algae, leaves, the human body, etc.
You would need to do some more strict testing and measuring to determine whether the majority of the smell in a pool is coming from urine or other organic materials.
Then how do you explain the smell of chlorine bleach straight from the bottle?
Gee, you mean a fresh pool that no one has even been in doesnt smell like Chlorine? I know that to be false.
Yep.
Odd little trivia- Disneys Pirates of the Caribbean ride has a unique odor- they use bromine, not chlorine to keep the water nice. And no one is urinating in that water.
Yep.
In fact after cleaning the toilet with bleach, then flushing, the bathroom smells like chlorine for hours- and sure we do urinate in the toilet, but not in that particular flush.
The YT is wrong.
Maybe if he had said- The stench of strong chlorine is exacerbated by urine to a large factor.
It isn’t diluted.
Yep, although @Sage_Rat is partially though not entirely right. Yes, chlorine has an odor. I can clearly smell it in the laundry room after adding bleach to a wash, or when cleaning with a disinfectant spray containing chlorine. Sometimes you can even faintly smell it in tap water (one reason I only drink spring water).
However, the smell of chlorine in an outdoor pool should normally be minimal to non-existent, especially if sanitized with a salt system instead of direct chlorination, and a more distinct smell, unless due to over-chlorination or shock chlorination, is likely to be due to the formation of chloramines. So while the YouTube video in the OP seems rather considerably exaggerated, it’s not entirely false.
Here’s another reference: