Toilet waste (black) water pipes are quite underused for their diameter so it's enough to just feed dozens of bathrooms' worth into a reasonable diameter you can still get at a hardware store. Sure, some will have trouble flushing if they all do that at the same time but not too serious.

As for drinking water, some high-rises feature tanks as part of their oscillation damping system anyway, and municipal water towers don't need to be placed much higher than customers to get decent pressure. I think it's not the amount but pressure of water at the ground floor that causes engineering challenges. The pumps and tank at the top help, though.