I don't flush condoms, not at my incall nor at a hotel. Why? It's horrible for the plumbing.
There are a few friends who will orgasm, run to the restroom and flush the condom down the toilet. When someone is that keen on trying to get rid of the evidence, there isn't much that I can do about it.
But at my incall, I take off the used condom and wrap it in toilet paper and throw it away. Same with the hotel.
Then, I take a very nice warm washcloth and clean off my fellow. I also do that at hotels, too!
I will say, just to add to the gross factor, if I'm in a hotel, I don't leave used condoms in the trashcan. If I'm having a busy time of it, I put the condoms in a trash bag and throw them away on my way out. I don't wish to have a bunch of those things in the trash can when the maid cleans up.
I use a LOT of condoms because of my alternative play. Going through a 1/2 dozen of them in one sitting isn't that unusual (imagination is a good thing!).
Even though I am a renter, I wouldn't do that type of harm to the property. And I use a TON of condoms on any given week.
I would just be embarrassed for a plumber to have to come over and deal with that aftermath, in case of a flood or some sort of plumbing disaster.