I think sewer backup is a separate rider from full flood insurance (at least it is on my policy). Also, not to get political, but absent federal subsidy, the state of florida (somewhat important) is uninsurable at rates anyone could afford, not that it matters since the same is true of most of the gulf coast and eastern NC (not regions you want to infuriate as a republican)
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