Understanding Your Pressure Tank and Switch: The 30/50 Rule Explained
If you've ever looked at the pressure gauge on your well system and wondered what the numbers actually mean, or heard a technician mention "30/50" and nodded along without really knowing what it referred to, this is the piece that connects those numbers to what's actually happening in your system.
The Tank and Switch Work as a Pair
A private well system doesn't just pump water straight from the well to your faucets on demand — it relies on two components working together: the pressure tank, which stores a reserve of pressurized water, and the pressure switch, which tells the pump when to turn on and off based on that stored pressure. The tank holds a cushion of compressed air (behind a bladder or diaphragm) that gets compressed further as the pump pushes water in, and released as household fixtures draw water back out. The switch watches the pressure in that system and answers one question, over and over, all day: has pressure dropped enough that the pump needs to run again?
What "30/50" Actually Means
The numbers refer to two pressure points, measured in pounds per square inch (psi), that define when the pump turns on and off:
- Cut-in pressure is the point where pressure has dropped low enough that the switch tells the pump to start running again — in a 30/50 system, that's 30 psi.
- Cut-out pressure is the point where the tank has been refilled enough that the switch tells the pump to stop — in a 30/50 system, that's 50 psi.
A 30/50 setting — cutting in at 30 psi and cutting out at 50 psi — is the most common default for residential well systems, particularly single-story homes with shorter pipe runs. Some systems use a 40/60 setting instead, typically homes with taller structures, longer plumbing runs, or higher water-pressure demands, where the extra 10 psi at each end helps maintain adequate pressure throughout the house. Either setting is a normal, intentional design choice — what matters is that your system is actually cycling within its intended range, not which specific numbers it uses.
Reading Your Gauge: What Normal Looks Like
If your system has a pressure gauge (most do, usually mounted near the tank), normal operation looks like a slow, steady climb from the cut-in number up to the cut-out number as the pump runs, followed by a slow, steady decline back down toward cut-in as household water use draws the tank back down — then the cycle repeats. That rise and fall is expected; a gauge that's always sitting at nearly the same number rather than swinging between roughly two points is unusual, and a gauge that's swinging wildly, dropping fast, or never seems to reach the expected high point is worth mentioning when you request service.
Why Your Pump Might Run Constantly
A pump that doesn't seem to shut off — running continuously rather than cycling between cut-in and cut-out — usually points to one of a few things: a switch that's failed and isn't signaling the pump to stop, a leak somewhere that's preventing the tank from ever reaching cut-out pressure, or in some cases a pump that's lost its ability to build pressure at all. This isn't a symptom to wait out; a pump that runs continuously is a pump under sustained stress, and it's worth requesting service before it fails outright. See pressure switches for more on what causes a switch to stop signaling correctly.
Can You Adjust the Switch Yourself?
This is worth being direct about: the pressure switch is a component wired directly into your system's electrical circuit, and adjusting its setting involves working inside a live electrical enclosure. That's not a homeowner-safe task, and it's not something this page is going to walk through — not because the concept is complicated, but because getting it wrong risks both a shock hazard and further damage to the pump or switch. What is homeowner-safe is reading the gauge and describing what you're seeing — the numbers it's cycling between, whether it's holding steady or swinging, whether the pump seems to run longer than it used to. That description is genuinely useful information to pass along when you request service, even though the adjustment itself isn't something to attempt on your own.
When the Numbers Don't Match What You Expect
If your gauge is cycling well outside a 30/50 or 40/60 range, staying at one number without moving, or you simply don't know what range your system is supposed to run in, that's worth having looked at rather than guessing. A switch that's drifted out of its correct range, a waterlogged tank throwing off the whole cycle, or a pump struggling to reach pressure can all produce a gauge reading that doesn't match what it should. See pressure tanks for how a failing tank can throw off the whole cycle even when the switch itself is working correctly.