I was leaving town for 2 weeks and this freeze storm was about to blow through. I shut off water at the main and opened all bathroom and outdoor faucets to drain.
The hot water heater is in the attic. I left the gas hot water heater on. I didn’t shut off the cold supply valve because the main was off, and it’s not easy to get to in the attic. I left cold and hot taps open when I left the house, no water was coming out, but when I opened the hot faucet it did occasionally sigh for a few minutes. The temp dropped from 65 to 12 degrees Fahrenheit later that day.
I’ve read about siphoning and pressures. I felt like if I had both hot and cold faucets open then that should not allow a vacuum or an over pressure situation and so the tank should remain full of water.
I’m really stressing about this and not enjoying my vacation worrying that leaving the faucets open and not shutting the water in valve off was bad.