Flag: using "whether" in a sentence with "or not"

[ccoVeille]

whether implies the alternative, so writing this is invalid

Invalid	Valid
I wonder whether the water is cold or not	I wonder whether the water is cold
	I wonder if the water is cold or not

[hippietrail]

Wow I'd never considered this wrong before. I'm looking for whether it's in any style guides (or not). (-:

But if stylistic redundancy is something to flag it reminds me of the recently common redundant use of "both" instead of "the two" which I'll now consider writing up an issue for.