Toilet flow - something is wrong

I'm happy for you that it has resolved after all. The problem is, of course, that it could actually be that an unfavorably planned sewage pipe from the guest WC keeps getting clogged for you. You also can't tell every guest, please only make small poops. So I would definitely take another closer look to see if there is a bottleneck somewhere. Theoretically, you can still check that on the piping plans. For example, a curve and supply line directly behind the downpipe or something like that.

Would be good to leave it for now, you apparently solved the problem for the time being. Still, of course, keep an eye on the whole thing. You can't really do much without much effort at the moment anyway. Always rinse thoroughly with plenty of water

So far, we have actually always only used the [Sparspülung]. But I will leave it be for now. However, the flushing is now set to full-pull flushing.

Pouring in a little dishwashing liquid now and then is supposed to help too...

As a secret tip, I read about baking powder together with vinegar. I poured that into the oven the day before yesterday. Maybe that helped too.

At our workplace, the small flush was blocked and now we can only flush at full power, otherwise the pipes get clogged. But in a new building (wasn’t it, right?) something like that shouldn’t happen.