SOLVED. FOUND: 70's Superman novelization [s]

[Fel]

My wife remembers reading a novel about Superman written in the seventies/early eighties. It was set in Superman's future after he lost his powers and was living as regular Clark Kent. It turned out that Lex Luthor had bought all the porcelain companies in America and introduced Kryptonite into the forms so Superman would slowly lose his powers every time he took a shower.

[Tab]

Does your wife remember if the novel was a TV or movie tie-in?

Anything about the cover?
Was part of a Superman novel series?

[Fel]

Superfolks by Robert Mayer. A pastiche/satire of the superhero genre, with only the Marvel family getting different names.

[Bargle]

Superfolks
Clicky for the book.