Pressure Tank — Well System Glossary
A pressure tank stores pressurized water from the well pump and maintains consistent household water pressure between pump cycles.
The pressure tank is one of the two most important components in a private well system — the other being the pump. Understanding what it does and how it can fail helps you identify problems early, before a failed tank leads to a damaged pump.
What a Pressure Tank Does
When your well pump runs, it pushes water up from the aquifer into the pressure tank. Inside the tank is a rubber bladder or diaphragm that separates the water chamber from an air chamber that is precharged to a specific pressure (typically 2 PSI below the cut-in pressure of the pressure switch). As water fills the tank, the air in the chamber compresses. When you open a faucet, this compressed air pushes water out of the tank and through your home's plumbing — without the pump needing to start.
The result: your pump runs in long, efficient cycles instead of starting every time you open a tap. This dramatically reduces wear on the pump motor and extends its service life. A properly sized and maintained pressure tank can add years to a well pump's operational lifespan.
Types of Pressure Tanks
Modern residential pressure tanks use a butyl rubber bladder to separate the air and water. The bladder prevents the air charge from dissolving into the water over time — a problem that plagued older galvanized steel tanks, which had no separation between the air and water and required periodic recharging. Bladder tanks are now the industry standard and require far less maintenance than galvanized tanks.
Recognizing Pressure Tank Failure
The most reliable sign of pressure tank failure is the pump short cycling — turning on and off rapidly, sometimes every few seconds. This happens because a failed bladder can no longer hold the air charge, so the tank fills entirely with water and loses its buffering function. Without the air cushion, the pump must activate every time pressure drops even slightly.
Other signs include: water pressure that spikes when the pump starts and drops quickly, water coming out of the Schrader valve (the air valve on the tank) when you press the pin, and a tank that sounds or feels completely solid and full when you knock on it. A healthy tank should sound slightly hollow in the upper portion.
Maintenance and Replacement
The main maintenance task for a bladder pressure tank is checking the precharge air pressure annually. With the system fully depressurized, use a standard tire gauge on the Schrader valve. The reading should be 2 PSI below your pressure switch's cut-in setting. If air pressure is correct but you are still experiencing short cycling, the bladder has likely failed and the tank needs replacement.
Most bladder pressure tanks last 8 to 15 years. Replacement cost typically runs $300 to $800 including parts and labor. When a tank fails, replacing it promptly is important — short cycling puts significant stress on the pump motor and can turn a $500 tank replacement into a $2,000 pump replacement if left unaddressed.