[hammock]

What they are calling “per capita domestic water use” is the per capita public+self supplied, which is not the same as home use. They sort of hand-wave over “most of this is used at home” but really it is inclusive of not only lawns (which are bigger in the US) but commercial use of water as well- commercial landscaping (far more in the US than in Europe) and other business use

Plumbing fixtures are also more regulated in the EU but I suspect this is a small portion relative to landscaping.

[Maxion]

As with most things, I think there's multiple things. US home also tend to be larger, meaning the hot water line is longer from the tank to the shower. Most americans I know tend to leve the shower running before they get in so it "warms up". I've never been in a European shower that's required that.

[wongarsu]

Not just the bigger homes, from what I can tell in US home construction the length of the hot water pipe isn't a consideration at all, while it is a common consideration in European homes. In Europe (vast overgeneralization incoming) it's not unusual to have a boiler or a tankless water heater directly in the bathroom to keep the line short, and then have the kitchen close by. Having multiple water heaters per home is also completely normal and a common solution if the kitchen is too far from the bathroom or multiple bathrooms are far from each other. In the US the norm seems to be to just stick a big boiler in the basement or somewhere else out of the way, then run hot water lines everywhere. Maybe in part due to the added effort of running 220V lines in a 110V country

[ajmurmann]

"I've never been in a European shower that's required that." Unfortunately, my parents' home in Germany does require this.