If the house has a sump pump, another rider is needed for failure or backup through it, which happened to me in 2010. It rained heavily for quite a while, but that's not the reason we had a problem- The storm came through on a West to East line, not angled as usual from Northwest to Southeast, which put a huge strain on the ability of the Milwaukee River to contain the water that entered directly and from runoff. I had a window open while it rained and the problem wasn't due to the amount of rain that fell here, it was from the rain that fell about 15 miles to the North in a line that crossed the river and created a surge in water level that the river and all of the streams and creeks were unable to handle without going over the banks. One of the creeks is about 50 yards to the West and the normal level is around 7' below the road but on that day, it was close to 15' higher than usual and as the rain fell, I realized that the sound of rain falling on pavement had changed to the sound of rain falling on water. I looked out and the creek had risen and the water line was in front of my house and moving higher. It eventually stopped two houses to the North of mine, but that's not the real problem- The first part of the storm stopped dumping on us around 4PM, but my problem was from the rain th at started around 9:30 coupled with the maple tree's tap root directly over my sewer lateral and the power in the area going out between 9:45PM and 4:25AM.
I now have a generator. Fortunately, I had both sewer and sump pump backup coverage, but when I called Acuity Insurance, I was told that the damage probably wouldn't be covered since it came in from two places. Wha, wha, whaaaat? I never heard about that before!
Check your policies, people- never assume anything.