Washerless faucets.

They may seem like a good idea to a plumber, but it's too hard to get water which is neither boiling hot nor ice cold.

And why does the shower control have to operate differently in every hotel I go to?

I was once having a shower at a motel, when the cold water suddenly stopped, and I found myself in a cascade of dangerously hot water. It was in a tub, so I fled to the far end and cried for help. Fortunately, my husband was with me, so he came in and turned it off. (I hate to think what would have happened if I'd been alone.)

I mentioned it to the desk clerk later, and he said, "A little piece of lime must've got in the control. We'll look at it."

What kind of system is it where 'a little piece of lime' leads to scalding a person?