Flushing the toilet when there's nothing in it but differently coloured water is a waste, but I understand why you have to do it in a social context. I would prefer not to needlessly strain my shitty pipes, but I prioritise other people not needing to know that I piss just like they do.
Anyways, this is a very obtuse way of asking how many times does a person have to come to your apartment before you can shamelessly not flush the toilet after (visibly) peeing?
I care about my water consumption. It might not mean much now, but it'll be great to build up a habit before the Water Wars start.
Get a toilet that is dual flush. One setting for piss and another for shit
Get a flushless/waterless urinal if the parts provide the use.
You can get a dual-flush conversion kit for your toilet, it replaces the flapper valve thing and the handle. And it's really adjustable so you can make sure it uses the minimum amount of water to flush your piss.
Or put a brick in the tank.