Okay, so the water in hotels that sucks at getting soap off (it doesn’t really, but it feels like it does) is softened water. It has been treated to remove calcium, magnesium, and other cations, to prevent scale buildup.

As I understand it skin feels slippery like it hasn’t removed the soap for potentially a few reasons. General consensus is that either you’re feeling whatever salt they put in the water to treat it, or you’re feeling the lack of those minerals. That is, you’re use to the water making your skin feel less slippery because of the various minerals in it, so the absence of those minerals makes it feel slippery. You get used to this eventually, but it’s annoying if you aren’t used to softened water.

The confusion comes in because in home water systems, you really only need a water softener if the water in the area is particularly hard. So it’s easy to associate softened water with hard water. Because you don’t really need to soften water that isn’t high in mineral deposits (unless you’re a hotel trying to minimize cleaning costs and are treating a fuckload of water centrally).

So you’re both right. It’s soft water because it’s been softened. And it’s been softened because it’s hard water. 😂