sometimes the main shutoff can break like mine did after 25 years. in
the off position of course. start these projects in the morning when
the hardware store is open late. my plumber came in and cut the old one
out of the 3/4" copper water line, replacing it with a nice lever
handled ball valve compression style installation. no "sweat". but he
was wet even with a plastic tarp. otherwise the underground main
shutoff is a must-dig-up when it breaks.