Your water heater also has a shut-off valve, usually on the cold water pipe above it. If the heater springs a leak (and they do, often at 3 AM), turn that off separately. Otherwise, your main valve will kill everything, including your hot shower.
Outside spigots (hose bibs) often have their own shut-off inside the house. If you don’t turn those off in winter, your pipes will freeze, burst, and you’ll be mopping your garage floor until spring. Yes, this happened to my uncle. Twice.
Mind-blowing statistic: A single burst pipe can shoot out 200 gallons of water per hour. That’s enough to fill a bathtub every six minutes. Your water bill will look like you bought a swimming pool.
