Having smoking and non-smoking sections in the same restaurant is like having peeing and non-peeing sections of the same pool.

As the CMC had read the rules when the water at pony-ville municipal pool had contained a dye when in the presence of urine it reacts to change the color of the water when those wonder in the second last panel those like the expressions of sweetie belle and apple bloom when in the last panel twilight wonders what she did to have a crowd give her the strange looks when she wondered of the dye being used when she relieved herself in the pool changing the water to a greenish tint.

Somewhere near the front gate there is a sign that reads,  
“welcome to our “ool”, you will notice there is no “p” in it, please keep it that way.”
 
… Also at some other point during the summer it was altered to read, “welcome to our “l”… “  
I will leave you all to deduce exactly why, and what the rest of the sign read as.

@Ferrotter  
I lost all desire to use hot tubs when I heard, second-hand from someone who said they knew a plumber who warned them how disgusting they all are, especially ones in hotels. Likened to a bacteria-filled petri dish. I don’t even like the idea of using a hot tub at someone’s house. Let alone one at a hotel.
 
Chlorine is indeed very volatile. Exposure to light also breaks it down. Lots of households have a spray bottle of a water/bleach solution for cleaning, but in fact they’re useless if they’re more than a day old. Chlorine breaks down in under 48 hours after mixing and loses its sterilizing power. Even if you can still smell it, it doesn’t mean it’s effective anymore.

@Vinyl Fluff  
Also dead skin. The foam on top of a hot tub is not soap or chlorine or a natural property of hot water, it’s mostly soggy flecks of dead skin. Unfortunately showers aren’t really much good for that. You have to soak about half an hour to really loosen up all the dead skin that will come off you that day. But a shower will reduce the amount somewhat.
 
Being in the hot tub will get the rest of it off you. And dead skin floats due to its contents of waterproofing fats called ceramides (hence why a film of it is on the surface of the hot tub, adding to the surface tension of the water and creating the foam). When you step out of the tub you pass through that layer of dead skin. It clings to you like you walked through a spider web. So shower when you get out of the hot tub. Ideally, take a long bath before you go to the hot tub, to remove your dead skin; then take a quick shower to remove your own film of reapplied dead skin after getting out of the bath; enjoy the hot tub and pool as long as you want; then when you’re done, most importantly, take another shower. Because you can be quite sure nobody else did all that, and you’re now covered in their dead skin if not some of your own (assuming you didn’t do all that either).
 
And to make it worse, hot tubs are usually under-chlorinated. Especially public ones. (And especially especially, ones in “good” places like luxury hotels.) Hot tubs are, as the name implies, hot. You can smell pool chlorine because it is volatile and evaporates into the air at a certain rate. Making it hot makes it evaporate faster. That means hot tubs should be heavily chlorinated if the water is to remain germ-free. People, especially luxury hotel guests, bitch about the smell and the irritation if the hot tub is properly chlorinated. And the management, especially in luxury hotels, wants the guests happy. So they tend to skimp on the chlorine. Government-run facilities like school gyms and town pools, where management is distant and unresponsive to “customers” who have no choice but to pay taxes and get whatever they get, tend to be a lot better.
 
So tl;dr, being pissed on won’t hurt you. Soaking in someone else’s ass flakes, in a tub that is hot and short on chlorine, and leaving that filth on you afterwards, could.

@dekutree64  

 
It’s not just dirt. It’s also whatever else you might have on you like sunscreen, that the showers are meant to wash off. While gross, urine is easier on the pool and the filtration system than other kinds of dirt, grime and muck.

I just noticed something… you know how a lot of pools have signs saying to shower before you get in? I bet that’s not so much to wash the dirt off your body as it is to trigger your water contact bladder response before getting in the pool.

Dem copy-and-pasted faces on Sweetie Belle and Apple Bloom

@Ferrotter  
+1
 
@PiMan  
I heard the same thing, although natural spas and thermal spas and stuff don’t have enough chlorine in them to do that. Probably why you can see old people sitting in them all day without ever getting out.

Just because it hasn’t been brought up yet, such dye does not exist IRL. It’s an urban legend spawned from a TV show.

Water’s too cold. I’m going over near Twilight where it’s warmer.

@cdcdrr  
Yeah yeah, not everybody does it. Clearly not I, as evidenced by me saying so in defense of such a statement.

@cdcdrr  
Nope. Not everyone. I’m sure that many people do but that doesn’t mean that everyone does. I also suggest you stop that too.

@cdcdrr  
Not everyone does it. It is also not a good idea because of how it reacts with chlorine (it can redden and irritate your eyes), creating cyanogen chloride, nitrogen trichloramine.  
In the ocean on the other hand, go ahead. No nasty chemical reactions there.

Urinating in the pool is like masturbation. Everyone does it, they deny it, and society shames them into not doing it publically.