Industry gatherings are where contractors compare notes. The ACHR News photo gallery on the inaugural HVAC Contractor Forum notes that more than 200 HVAC professionals attended the event, held Nov. 2-4, to "network and learn from some of the best in the industry." Much of what a good service tech knows comes from repeated measurement, and a homeowner with a tire gauge can do a version of that measuring on a well system.
Start With the Air Side
A typical residential well tank has two sides, water and air, separated by a bladder or diaphragm. The air side acts as the spring. When you open a tap, that compressed air pushes water out, so the pump does not have to run. If the air pressure drifts low, the tank holds less usable water per cycle, and the pump starts and stops more often than it should. Short cycling is hard on the motor, the pressure switch, and the contacts inside the switch.
Gather Your Numbers First
Find the pressure switch and read the label or the settings. You are looking for two values: the cut-in pressure, where the pump starts, and the cut-out pressure, where it stops. Those settings vary from house to house, so use your own switch as the reference, not a number from a forum post. You also need a low-range tire gauge, a bicycle pump or small compressor for adding air, and a bucket for any water that comes out of the valve.
Before touching anything, switch off the pump breaker. Open the highest faucet in the house, then a lower one, and let the system drain until flow stops. The water side of the tank should now be at or near zero pressure, which is the only condition in which the air reading means anything.
Read the Precharge
Remove the cap from the tank's air valve, which looks and works like a tire valve. Press the gauge on squarely and read it. The precharge should sit a little below the cut-in pressure. A common rule of thumb is a couple of psi below cut-in, so a switch that starts the pump at 40 psi would normally be set near 38 psi. If your tank's documentation gives a different precharge, follow that instead.
If the reading is low, add air in small amounts and check again after each addition. Overfilling is a real mistake, because too much air leaves the tank with too little drawdown and the pump cycles on small demands. When you are done, cap the valve and check for leaks with a little soapy water. A slow bubble at the valve is a fitting problem. A steady leak that keeps the reading dropping points to the valve itself.
When Air Is the Wrong Fix
If you press the valve and water sprays out, or if the tank keeps filling with water even after you add air, the bladder has probably failed. Adding air will not cure that. The water side is leaking into the air side, and the tank needs replacement or a service call. This is the point where a homeowner should stop troubleshooting and let a qualified well contractor take over.
Where the Multimeter Fits
A multimeter earns its place in two places. First, confirm the pump circuit is dead at the breaker and at the pump or switch before you open anything. Second, with power removed, you can check continuity across the pressure switch contacts to see whether the switch is closing and opening as expected. Voltage checks with power on belong to a licensed electrician, and so does any work inside the switch housing.
Log the Cycle
Write down the date, the precharge reading, the cut-in and cut-out settings, and the tank's location. Then, on a day with no other water use, open one faucet and watch the pump for a few minutes. Note how many times it starts and how long it runs each time. Repeat that test each season. A stable tank gives you a flat record. A tank that starts losing precharge will show a pattern in your notes long before the pump fails.
The people at the forum will argue about equipment and methods, and that conversation is useful. Your well tank is quieter, but it will give you the same kind of answer if you measure it, write the numbers down, and compare them next season.