Wait, a $600 descaling bill? That part jumped out at me because I have never heard of anyone paying that. Did a plumber actually come out and do the flush for that price, or was it some kind of repair on top of the flush? Around here you can buy a pump and a bucket of vinegar and do it yourself in an hour, so I'm trying to figure out what they charged you for. Also, how hard is your water exactly? If it's chewing up a tankless that fast, I'd worry about what it's doing to your fixtures and your coffee maker too. Six months feels way too soon to already be dropping that kind of money on upkeep. What did the installer tell you about the yearly maintenance before you bought it?

Man, that Nashville story hits close to home. I just use Weather Underground's hourly tab and cross it with the NWS point forecast for my zip, then I won't even call the plant unless the rain chance stays under 20 percent for the whole window. If the two don't agree, I push the pour. Not worth rolling the dice on a 40 yarder.