You can feel or hear itCommon

What size pressure tank do I need?

Big enough that your pump runs at least a minute per cycle, and two minutes if the motor is above three-quarter horsepower. That run time is what lets the heat from starting dissipate, and it is the number that actually decides tank size. Compare drawdown, not the gallons on the label.

Also covers what size well pressure tank · pressure tank sizing · how big a pressure tank do I need

Minimum run time: 1 minute per cycle
Above ¾ horsepower: 2 minutes per cycle
What actually matters: Drawdown, not total gallons
A "32-gallon" tank may deliver: Around 8–20 gallons of drawdown
An undersized tank: Recreates the short-cycling problem

What this means

What this means for you

Two ways to know for sure.

The single most useful thing to know when tank shopping is that the number on the box is not the number that matters. Tanks are sold by total volume, but what you actually get between pump cycles is drawdown, which is a fraction of it and varies with the model and your switch range.

Two tanks both labeled 32 gallons can deliver very different amounts of usable water. Compare drawdown.

Most of what’s on this page comes down to two things you can check yourself, today, for almost nothing:

Start hereGround truth

Measure your pressure before you buy anything

Screw a gauge onto an outside tap and open it fully. The reading is the first thing a plumber will ask you for, and it rules out most of the causes on this page on its own.

A pressure gauge is an inexpensive hardware-store part.

What your reading meansUnder 50Below the range to aim for50 to 60The range to aim forOver 80Above the code ceilingThe 80 PSI ceiling is code, not opinion: the plumbing code caps static pressure there and requires a regulator above it.

Free

Turn the reading into a decision

Two calculators do the arithmetic: what your pre-charge should be, and whether your tank is big enough for the pump you already have.

Pre-charge rule: 2 PSI below cut-in
Min run time: 1 min per cycle

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Pressure Fix

Size my tank

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Quick questions

The questions people ask next

What is drawdown?

The usable water you actually get out of the tank between the pump shutting off and starting again. It is always a fraction of the tank’s total volume, because most of the tank is the air spring that does the pushing.

Why does run time decide the size?

Because the damage from short cycling is heat. Each start heats the motor windings, and a pump needs a minute of running to shed that heat. A tank big enough to guarantee that minute is a tank big enough, full stop.

I added irrigation and now it short cycles. Is that the tank?

Very likely. The system was sized for the old household. Adding irrigation without upsizing the tank can multiply how many times the pump starts each day.

Can I add a second tank instead of replacing?

Yes, and it is a legitimate approach. Two tanks plumbed in parallel add their drawdown. Worth pricing both ways, since a single larger tank is sometimes cheaper than a second one plus the plumbing.

Does a bigger tank raise my water pressure?

No. It gives you more water between pump starts, which is a different thing. Pressure comes from the switch settings and the pump.

Pages that often come up alongside this one.

These are likely causes based on what people commonly describe, a place to start, not a diagnosis, and not medical advice. For anything health-related, a certified lab test and your local health authority are the ones to trust.