A well system that works fine most days can still be failing. The first sign is often the pump itself. It starts, runs for a few seconds, stops, and then starts again a minute or two later even though nobody has opened a tap. Left alone, that pattern wears out the pump motor, the pressure switch contacts, and the tank diaphragm or bladder. Catching it early is mostly about knowing what normal looks like and reading a few simple signs.
What normal cycling looks like
A pressure tank holds a cushion of air above the water. As you draw water, the air pushes the water out, and pressure falls slowly. When pressure reaches the pump's cut-in setting, the pump starts and refills the tank until it reaches the cut-out setting. A healthy system runs for a reasonable stretch each time, then stays quiet until the next real demand. If you have a household member who showers and runs a washer, the pump should not be short-cycling during those uses. It should run longer and then rest.
The signs that show up first
Watch for the pump starting and stopping when no water is running, a pressure gauge needle that swings noticeably between readings, faucets that sputter or spit air after the pump has just run, and a pump that feels warm or hums without much water moving. Any one of these can have more than one cause, so do not assume the tank is the problem until you have checked the rest of the pattern.
Tell a tank problem from a leak or a bad check valve
Two simple observations separate the common causes. First, with all faucets closed, watch the gauge right after the pump shuts off. If pressure drops fast, within a few minutes, water is leaving the system somewhere, through a leaking fitting, a faucet that is not fully closed, or a check valve that is not holding. Second, if the pressure holds steady for a while and the pump then restarts after a longer rest, the problem is more likely the tank losing its air charge, so the tank fills with water and has no cushion left.
Check the air charge yourself, carefully
Before you touch anything electrical, switch off the breaker that feeds the pump. Open a faucet near the tank and let the system drain until the flow stops and the gauge reads zero. Then find the air valve on the top of the tank, which looks like a tire valve. Put a tire-type gauge on it and read the air pressure. Compare that reading with the pump's cut-in setting on the pressure switch. The usual guidance is that the empty tank should sit a little below the cut-in pressure, commonly about 2 psi below. If the reading is far lower, or the valve shows no air at all, the tank is either losing air or already full of water. Add air only with the tank drained and the pump off, and recheck. If you cannot get a steady reading, or the air keeps leaking out, stop there and call someone.
Do not run the pump dry. If the gauge drops to zero while the pump is still running, shut the breaker off right away.
What to ask the technician
When you call someone, describe the cycling pattern in plain terms: how long the pump runs, how long it rests, and whether pressure drops after shutoff with no faucet open. Ask them to check the tank's air charge with the pump off and the tank drained, to test the pressure switch contacts for wear, and to check the check valve and any fitting near the pump. Ask whether they will replace a bladder or the whole tank, and what they will do if the diagnosis is a leak instead. A good answer names each check and what it rules in or out. A vague answer that jumps straight to replacing the pump is a reason to get a second opinion.
If you need a provider who handles well systems and treatment equipment, the directory of water treatment providers in Missouri is a place to start your list, and you can compare how each one describes its diagnostic steps before you commit.
When to stop waiting
If the pump is cycling many times an hour, if the gauge swings wildly, if the pump runs without building pressure, or if the pump or the wiring gets hot, shut it off and get help. Early short cycling is usually a cheap repair. Left alone, it can turn a tank or switch fix into a pump replacement.