Sump failure is flood damage. At least it was for me when the power failed and my sump failed flooding the finished basement. If it's stormwater damage, its flood damage.
I am 99% sure I have the sewer and drain backup insurance. I guess that would cover a sump . . .
My last rental house came with toilets that ran backwards 
so I'm pretty sure we have it now.
EDIT: 75k of water backup insurance 
