What was Samantha's maiden name before she married Darrin?In a Black and White Dick York as Darrin episode,Endora was asked what her name was,and Endora replied "Mrs.Waters".So was Waters Samantha's maiden name?

I dont think she has one.

Endora was just kidding when she said "Waters" was her last name - due to the water main break she caused to help Ed Wright become councilman. In the earlier episode, "Mother Meets What's-His-Name", Endora told Darrin he'd never be able to pronounce her last name. Since we never found out what Maurice's last name was, and since they were still technically married, I would assume that Endora's last name was still the same as Sam's maiden name.

At no time was it ever stated what Samantha's maiden name was on Bewitched.
In the Al Hine Novel about Bewitched in 1965 it was said to be Dobson but the book nor anything in counts, only what was actually in the TV episodes themselves exists in these regards.

Larry Tate :)

What was Samantha's maiden name before she married Darrin?In a Black and White Dick York as Darrin episode,Endora was asked what her name was,and Endora replied "Mrs.Waters".So was Waters Samantha's maiden name?

that novel is non-canon. non canon means it isn't part of bewitches continuity.