The pressure tank is the quiet part of a well system that gets blamed last and causes plenty of service calls. If your pump clicks on every time someone washes their hands, or the pressure gauge swings wildly, the tank is the first suspect.
What the tank does
Most modern tanks have a rubber diaphragm or bladder with compressed air on one side. As the pump fills the tank, the air squeezes and pressure rises until the switch shuts the pump off. When you open a tap, the air pushes water out and the pump stays off until pressure drops to the cut-in setting. The water delivered between pump starts is called drawdown. A tank with good drawdown means fewer starts, which saves the motor and smooths out pressure (Amtrol Well-X-Trol manual).
How a tank fails
- Lost air charge. Air slowly leaks out through the valve or the diaphragm. The tank fills almost completely with water, drawdown shrinks to almost nothing, and the pump short cycles.
- Ruptured bladder. Water ends up on the air side. Pressing the air valve stem spits water instead of air.
- Corroded shell. Rust streaks, pinhole leaks or a damp floor around the base.
Dry taps or a pump that won't quit? One call gets you to a licensed pump installer near you. (405) 536-9841
Re-charge it or replace it?
Tank makers set the empty-tank air charge about 2 psi below the switch's cut-in pressure. A 40/60 switch, for example, pairs with a 38 psi precharge. The adjustment is made with the pump off and the tank drained (Amtrol). But that same manual warns against pumping air back into a tank that has been in service and has lost its charge. A shrinking pump cycle can mean internal corrosion, and re-pressurizing a weakened tank risks a rupture. Amtrol says only licensed professionals should check or recharge a tank's precharge. That is why installers often replace an old waterlogged tank instead of topping it up.
Sizing the replacement
A bigger tank stores more water between starts, so the pump runs longer and less often. The installer will weigh your pump's flow rate, the switch settings and the space available. On a well serving livestock or irrigation as well as the house, the right answer may be more than one tank on a shared header. The manufacturer also recommends a relief valve at the tank in case the pressure switch sticks and the pump never shuts off.
Where the tank lives matters
Many rural OKC systems keep the tank in a small well house. OWRB's owner guide says to keep a well house protected from freezing and pests, and to keep chemicals and fuel out of it (OWRB). A tank in a building that drops below freezing on a hard January night can split. Amtrol's manual says its tanks shouldn't be run where they can freeze. If yours is in an unheated shed, ask about a heat source.
Dry taps or a pump that won't quit? One call gets you to a licensed pump installer near you. (405) 536-9841
Signs to call now
- The pump starts every few seconds while water runs.
- Water comes out of the air valve.
- The tank is rusted through, leaking or bulging.
- The pressure relief valve is dripping or discharging.
Short cycling cooks pump motors. A tank swap is a much smaller job than replacing the pump it was protecting.
FAQ
What should my pressure tank be set to?
Tank makers like Amtrol set the precharge 2 psi below the pump's cut-in pressure, measured with the tank empty and the pump off. A 40/60 switch pairs with about 38 psi.
Can I just add air to my old tank?
Amtrol's manual says not to re-pressurize a tank that has lost air or shows a shorter pump cycle, because the cause may be internal corrosion. Have a licensed installer look at it.
How often should the tank be checked?
The manufacturer recommends a licensed professional check the whole system, tank included, every year, and more often as it ages.