Why does my well pump turn on and off rapidly?

Short cycling almost always means the pressure tank has lost its air charge or its bladder has failed, leaving no cushion. It is urgent because rapid cycling is what burns out pumps.

What pressure should a well pressure tank hold?

The air precharge, measured with the pump off and water drained, should sit 2 psi below the pressure switch's cut-in setting: 28 psi for a 30/50 switch, 38 psi for a 40/60.

How long do well pumps last?

Submersibles commonly run 10 to 20 years; jet pumps somewhat less. Short cycling, sediment, and frequent dry running are what shorten the number.

Why do I lose water pressure for a moment before it recovers?

That sag-then-surge is the pressure band in action: pressure falls to cut-in, the pump starts, and pressure rebuilds. A wide or low band, a waterlogged tank, or a clogged sediment filter exaggerates it.

Well Pumps and Pressure Tanks: How They Work

Page last reviewed: August 2026 · Reviewed by Harold R. Bennett, retired home inspector

A private well system has three characters: a pump that lifts water, a pressure tank that stores a cushion of it under pressure, and a switch that referees between them. Understanding the well pump pressure tank partnership explains almost every pressure complaint a well house produces, and it turns short cycling, the system’s most expensive bad habit, into a five-minute diagnosis. This reference covers the machinery and its care.

The pumps

Submersible pumps, the modern standard for drilled wells, hang down the well on a drop pipe, pushing water up from below. Efficient, silent, long-lived (10 to 20 years is routine), and out of sight, which is also their weakness: service means pulling the string.

Jet pumps sit above ground, in the basement or well house, and pull water up, a shallow-well configuration handling lifts to roughly 25 feet and a deep-well two-pipe version reaching further at declining efficiency. Accessible and cheap to service, noisier, and dependent on holding their prime.

Between pump and house sit two humble guardians worth knowing: a check valve (or foot valve) that keeps the column from draining back down the well, whose failure shows up as a pump running to hold pressure overnight, and, on many systems, a sediment filter that quietly becomes the main pressure suspect when it loads up.

The pressure tank: why the system has a cushion

A pump that started every time anyone opened a tap would start hundreds of times a day and die young, since motor starts, not run time, are what wear pumps. The pressure tank is the fix: a steel vessel holding a captive air charge, in modern tanks behind a butyl bladder or diaphragm, that compresses as the pump packs water in. Open a tap and the compressed air pushes stored water out, no pump start required; only when pressure falls to the switch’s cut-in point does the pump run, refilling to cut-out and shutting down.

The pressure switch defines that band, commonly 30/50 or 40/60 psi, and the tank’s air precharge must be tuned to it: 2 psi below cut-in, checked with a tire gauge at the tank’s valve stem with the pump off and pressure drained. That one number is the system’s tuning fork.

Short cycling: the diagnosis worth memorizing

The signature failure: the pump snaps on and off every few seconds while water runs. The cause, nearly always, is a tank that has lost its cushion, either the air charge has leaked down or the bladder has torn and the tank has waterlogged. The test takes a minute: tap the tank top and bottom (a waterlogged tank sounds dull and full high up), or press the valve stem, where water instead of air convicts the bladder outright. A failed bladder means a new tank; a merely low charge means air it back to spec and watch whether it holds.

Short cycling is urgent rather than cosmetic because every needless start shaves pump life, and pumps cost multiples of tanks. The same logic explains chronic pressure sag complaints: an undersized or failing tank narrows the cushion, making the house feel every pump cycle, one branch of the broader low pressure diagnostic.

The rest of the failure catalog, briefly

Pump runs but no water: lost prime (jet pumps), a failed check valve draining the column, a dropped water table, or a pump at end of life. Pump will not start: switch contacts (burned or nested contacts on the pressure switch are a classic), breaker, or control box capacitor on submersibles. Pressure gradually weaker over months: loading sediment filter, scaling pipe, or a tiring pump. Air spitting at faucets: a water table drawing down to the pump, or a bladder shedding its charge into the water. And any electrical or down-well work belongs to a pump contractor, both for safety and because pulling a submersible is genuinely two-person, equipment-assisted work.

The maintenance short list

Annual: check the precharge and switch band, exercise the tank tee’s valves, listen to a full cycle for crisp starts and stops, and change sediment cartridges on their schedule. Same visit, run the water testing panel the well itself is due for, since iron and sediment are as much equipment issues as water quality ones. Keep the well cap sound and the wellhead grade shedding water away, and log the system’s normal, band, precharge, and cycle behavior, because every future diagnosis starts from knowing what normal was.

The bottom line

The pump lifts, the tank cushions, the switch referees, and the precharge keeps the peace. Check the air charge yearly, treat short cycling as the emergency-in-slow-motion it is, and the quietest utility on the property will stay that way for decades.