Well Pressure Tank Sizes Explained
Choosing the wrong size destroys your pump. Terry Foster Jr., MD Master Plumber #98433, explains how to size a pressure tank correctly for Southern Maryland well systems.
Terry's Verdict
"An undersized pressure tank is the single most common cause of premature pump failure. Most homeowners are surprised to learn their 20-gallon tank should be a 44-gallon tank. Size matters more than most people realize."
Pressure Tank Size Comparison
| Tank Size | Drawdown (usable gallons) | Best For | Pump Cycles / Hour |
|---|---|---|---|
| 20-gallon | ~5 gallons | 1–2 person household, low demand | Up to 100+ (too many) |
| 32-gallon | ~8 gallons | 2–3 person household | 40–60 |
| 44-gallon | ~11 gallons | 3–4 person household (recommended minimum) | 20–30 |
| 86-gallon | ~22 gallons | 4–5 person household, irrigation | 10–15 |
| 119-gallon | ~30 gallons | Large households, constant pressure systems | 5–10 |
Why Tank Size Matters
A pressure tank stores a small amount of pressurized water between the pump and the house. When you open a faucet, water flows from the tank until the pressure drops to the cut-in point, then the pump starts. The "drawdown" — the usable water between cut-out and cut-in pressure — determines how often the pump cycles.
A pump that cycles more than 100 times per hour is being destroyed. The motor windings overheat, the bearings wear, and the pump fails years early. We see this constantly with undersized tanks.
The 44-Gallon Rule
For a typical 3–4 person Southern Maryland household, a 44-gallon tank (11 gallons drawdown at 40/60 PSI) keeps pump cycling in the safe range. Many homes we service have 20-gallon tanks installed by the original builder — the minimum code requirement, not the right size for the household.
Upgrading from a 20-gallon to a 44-gallon tank is one of the best investments a well owner can make. It can add years to pump life.
Waterlogged Tanks — The Most Common Problem
A pressure tank that has lost its air charge (waterlogged) provides almost no drawdown — the pump cycles on and off every few seconds. This is the most common pressure tank problem we see.
Signs your tank is waterlogged:
- Pump runs constantly
- Pressure fluctuates rapidly
- You can hear the pump clicking on and off every few seconds
A waterlogged tank needs replacement — the bladder or diaphragm has failed and cannot be repaired.
Which Size Is Right for You?
Only appropriate for 1-person households with very low demand — not recommended for most homes
Minimum for a 2-person household
Recommended minimum for 3–4 person households
RecommendedRight for 4–5 person households or homes with irrigation systems
Large households, constant pressure system upgrades
Frequently Asked Questions
How do I know if my pressure tank is the right size?
Listen to your pump. If it cycles on and off more than once per minute during normal use, your tank is undersized or waterlogged. We can check the drawdown and cycling rate during a service call and recommend the correct size.
How long does a pressure tank last?
A quality pressure tank (Amtrol, Well-X-Trol) lasts 10–15 years. Tanks fail when the bladder or diaphragm ruptures, allowing water to contact the air charge. Signs of failure: pump short-cycling, waterlogged tank, visible rust or corrosion on the tank body.
What does it cost to replace a pressure tank in Maryland?
A pressure tank replacement in Southern Maryland varies depending on tank size and location. We carry common sizes on our trucks for same-day replacement. Contact us for a free estimate.
Can I add a second pressure tank to increase drawdown?
Yes — adding a second tank in parallel doubles the drawdown without replacing the existing tank. This is a cost-effective option when the existing tank is relatively new and in good condition. We assess the existing system before recommending this approach.
What is the difference between a bladder tank and a diaphragm tank?
Both use a flexible membrane to separate the air charge from the water. A bladder tank has a removable bladder; a diaphragm tank has a fixed membrane. Both work equally well — the distinction is mainly relevant for servicing. We install Well-X-Trol (Amtrol) tanks, which are the most reliable brand in the market.
Is Your Pressure Tank the Right Size?
Terry will check your pump cycling rate, drawdown, and tank condition — and tell you exactly what size you need, with upfront pricing.