Your Pressure Tank and Switch, Explained: The 30/50 Rule
If you've had a well system for a while, you've probably heard the numbers "30" and "50" mentioned, usually in reference to your pressure gauge. Understanding what those numbers mean — and what the tank and switch are each doing to make them happen — makes it a lot easier to describe a problem accurately when something's not working right.
What the pressure tank does
The pressure tank stores water under pressure using a rubber bladder or diaphragm that separates a cushion of compressed air from the water itself. As the pump fills the tank, the air cushion compresses and stores that pressure; when a faucet opens anywhere in the house, the tank releases stored water under pressure before the pump even needs to turn on. This is what lets a well system deliver water without the pump running every single time someone opens a tap.
What the pressure switch does
The pressure switch monitors the pressure in the system and tells the pump exactly when to turn on and off. It's a small component, but it does the actual signaling — the tank stores pressure, and the switch decides when the pump needs to add more of it.
Where 30/50 comes from
Most residential well systems are set to what's called a 30/50 range: the pump turns on (the "cut-in" point) once pressure in the tank drops to 30 psi, and the pump turns back off (the "cut-out" point) once pressure climbs back up to 50 psi. Some systems are set to other ranges depending on the specific equipment and household needs, but 30/50 is the most common default across residential systems, including the ones typically installed in Tompkins County homes.
Why the range matters more than the exact numbers
What actually matters for a healthy system isn't whether your specific setup uses 30/50 or a different range — it's whether the system reliably cycles within whatever range it's set to. A system that consistently starts at its cut-in point and stops at its cut-out point is working correctly. A system that drifts, lags noticeably before starting, or fails to shut off at the expected point usually has a switch problem worth investigating — see pressure switches for what that typically involves.
How a bad tank or switch shows up on your gauge
A pressure gauge that swings wildly through a wide range, rather than cycling predictably between your system's cut-in and cut-out points, usually points to a tank that's lost its air charge and can no longer buffer pressure properly. A gauge that shows the pump running constantly without ever reaching the expected cut-out point often points to a switch that isn't signaling shutoff correctly. See why is my well pump short-cycling for how these two problems produce similar but distinguishable symptoms.
Other common ranges besides 30/50
While 30/50 is the most common default, some systems — particularly those with taller homes, multi-story properties, or specific equipment needs — are set to other ranges like 40/60 or 20/40. A higher range delivers more pressure at the top of a tall system but also puts more stress on tank and pipe fittings over time; a lower range is gentler on the system but may not deliver adequate pressure to upper floors or long runs. None of these ranges is inherently "correct" — what matters is that your system's actual equipment (tank size, pump capacity, switch rating) was matched to whatever range it's set to, and that it holds that range consistently.
Can I check any of this myself?
Reading your pressure gauge and noting what it shows when the pump turns on and off is a genuinely useful homeowner-safe check — it's exactly the kind of detail that helps route a service request accurately. Actually adjusting the switch's settings involves electrical connections and isn't something to attempt yourself; that's a job for an actual service visit.
What to report when you request service
- Your gauge reading at rest, and roughly what it shows when the pump kicks on and off
- Whether the pump seems to run longer than it used to, or short-cycle more than normal
- Any recent changes — new fixtures, a recent pump swap, or a switch that's never been serviced