The valve you never touch until you need it
You've got water pooling under the kitchen sink, or a toilet that won't stop running, and you reach for the little oval handle under the fixture. It won't turn. Or it turns and nothing changes. Or it turns and now you've got water spraying from around the stem because the thing hasn't moved since the Clinton administration. This is one of the most common calls in Springfield homes, and it almost always happens at the worst time, mid-leak, with water already on the floor.
Shutoff valves are supposed to be insurance. You install them, forget them, and trust them to work the one time you need them. The problem is that trust is misplaced if the valve has sat untouched for ten or fifteen years. Mineral deposits build up inside, the rubber or gaskets dry out, and the metal itself can corrode from the inside where you can't see it.
Why this is especially common here
Springfield sits on water with a fair amount of hardness, pulled from the James River, Stockton Lake, and area wells. Hard water leaves mineral scale on everything it touches, and shutoff valves are no exception. Over years, that scale cements the internal parts together. A valve that looks fine from the outside can be essentially frozen solid on the inside.
Add to that the age of housing stock around here. A lot of Springfield neighborhoods, from the older sections near downtown and Rountree out through Galloway and parts of Battlefield, have homes built from the 1950s through the 1980s with original or early-replacement plumbing. Those valves are well past the point where anyone expects them to perform flawlessly. Even newer builds in Ozark or Nixa aren't immune, because a valve installed in 2005 that's never been exercised is already a candidate for failure.
Our freeze-thaw winters don't help either. Pipes and valves near exterior walls or in unheated crawl spaces go through repeated temperature swings. Metal expands and contracts, seals get brittle, and a valve that was marginal in October can fail outright during a January cold snap when you actually need it to stop a burst line.
More on this from The Shutoff Valve That Fails The Day It Is Finally Turned.
What to check before you need the valve
Twice a year, maybe when you change your furnace filter or check smoke detectors, go around and turn every shutoff valve in the house a quarter turn and back. Under sinks, behind toilets, at the washing machine, and the main valve where the water line enters the house. This keeps the internals from seizing and lets you find a bad valve on a calm Saturday instead of during an emergency.
While you're at it, look for green or white crust around the valve body, any dampness on the wall or floor nearby, and whether the handle feels gritty or stiff compared to the others. A valve that's noticeably harder to turn than its neighbors is telling you something.
If you find the main shutoff valve is the one that's stuck, that's worth addressing sooner rather than later. That's the valve that matters most, and it's usually the one people touch least.
What you can handle yourself
If a valve turns but weeps a little around the stem, you can sometimes snug the packing nut just behind the handle with a wrench, a small turn, not a hard crank. That often stops a minor seep. If a valve is simply stiff from disuse, gentle, steady pressure with channel-lock pliers wrapped in a cloth to protect the finish can sometimes break it free without damage.
What you shouldn't do is force a frozen valve with a pipe wrench or extend the handle with a cheater bar. Old brass and copper fittings crack under that kind of torque, and you can turn a stuck valve into a sheared pipe in about two seconds. If it doesn't move with reasonable hand pressure, stop.
When it's time to call a plumber
If the valve won't budge, if it's leaking around the stem even after a light tightening, or if you can see corrosion eating into the body of the valve itself, that's a job for a professional. Replacing a shutoff valve sounds simple, and sometimes it is, but on older galvanized or original copper lines, the valve is often soldered or threaded in ways that don't come apart cleanly. A plumber can also tell you whether the valve failing is a one-off or a sign that the rest of the supply line is in similarly rough shape.
The other reason to call sooner rather than later is timing. You don't want to discover a dead main shutoff valve while water is actively flooding your basement. Getting valves inspected and replaced during a routine visit, before there's an emergency, is far less stressful and usually far less expensive than an after-hours call during a burst pipe.