If you discount comet strikes and sudden global warming, then the worst-case scenario for us is that the plumbing isn't done when we arrive. That would mean no water inside the house, no showers, no clothes washing. We'd have to use the hose from our well to manage water by bucketfuls.
Our ace in the hole is the Cinderella. It's there, it runs on electricity that's already installed, and all it needs is to have its exhaust pipe put up. So there's no reason the toilet shouldn't be working. (For those interested, an English user guide is here.)
Bottom line: as long we have the toilet, we can live with outside water. Many houses on the archipelago don't have inside water (or inside toilets, for that matter). So we can handle the worst-case scenario. I still think we won't have to, but it's good to be prepared.