How to Choose the Right Submersible Well Pump

Buying a submersible well pump can feel complicated.

You’ll see specifications for GPM, horsepower, voltage, stages, wire configurations, well depth, and more—and choosing the biggest pump or highest horsepower isn’t necessarily the right answer.

The right well pump is the one that can deliver the amount of water your home needs at the pressure you want, from the depth of your well.

In this guide, we’ll break down the information you need to choose the right pump and explain what each specification actually means.

First: What Does a Submersible Well Pump Do?

A submersible well pump is installed below the water level inside your well.

Rather than pulling water from the well, the pump pushes water upward through the drop pipe and into your home's water system.

A typical residential well system may include:

• A submersible pump and motor
• Drop pipe
• Well wire
• Check valve
• Pressure tank
• Pressure switch
• Pressure gauge
• Tank tee and fittings
• Control box for certain motors

All of these components work together, but choosing the pump itself starts with a few important pieces of information.

1. Determine How Much Water You Need

Pump capacity is typically measured in GPM, or gallons per minute.

This tells you how much water the pump can deliver under a particular set of operating conditions.

A home with one bathroom and two occupants obviously doesn't have the same water demand as a large home with several bathrooms, irrigation, and multiple people using water simultaneously.

That means more GPM isn't automatically better.

Your pump should be sized based on both the water demand of the property and what the well itself can reliably produce.

Why your well's yield matters

Your well can only provide water at a certain rate.

Installing a pump capable of moving 25 GPM doesn't mean you'll actually have 25 GPM available if the well only produces 10 GPM.

Pumping water faster than the well can recover can cause the water level to fall significantly and, in some situations, expose the pump to damaging operating conditions.

That's why pump capacity and well capacity need to be considered together.

2. Know Your Water Level — Not Just Your Well Depth

This is one of the most common points of confusion.

If someone tells you:

“My well is 300 feet deep.”

that alone isn't enough information to properly select a pump.

We also want to know the water level inside the well.

Two measurements are particularly useful:

Static water level is the water level when the well has been resting and no water is being pumped.

Pumping water level is the water level while the pump is operating.

Why does this matter?

Because your pump doesn't necessarily have to lift water the entire depth of the well.

If a well is 300 feet deep but the pumping water level is 100 feet below ground, the hydraulic conditions are very different from a 300-foot well where the pumping water level drops to 250 feet.

3. Calculate Total Dynamic Head

This is where pump selection becomes much more accurate.

You'll often see pump performance charts refer to TDH, or Total Dynamic Head.

In simple terms, TDH represents the total resistance the pump has to overcome to deliver water where you need it.

For a residential well system, that can include:

Vertical lift + required pressure + friction losses

Pressure can also be expressed as feet of head.

A useful conversion is:

1 PSI ≈ 2.31 feet of head

So if your system requires 50 PSI:

50 × 2.31 ≈ 116 feet of head

Now imagine the pumping water level is approximately 100 feet below ground.

Before accounting for friction and other system factors, you're already around:

100 ft lift + 116 ft pressure = 216 ft of head

This is why simply knowing horsepower isn't enough.

4. Use the Pump Curve

Once you know approximately how much water you need and how much head the pump must overcome, you can look at the manufacturer's pump performance curve.

A pump curve shows how much water a particular pump can deliver at different amounts of head.

Generally:

As the amount of head increases, the amount of water the pump can deliver decreases.

That's why a pump advertised as a “10 GPM pump” doesn't necessarily deliver exactly 10 GPM in every installation.

Its actual performance depends on the system it's installed in.

Water Pumps Pro Tip: Don't choose a pump based solely on the GPM or horsepower printed in the product title. Check where your required flow and head fall on the manufacturer's performance curve.

5. Don't Choose Horsepower First

It's very common to shop for a well pump by horsepower:

“I need a 1 HP pump.”

But horsepower is only one part of the equation.

Two pumps with the same horsepower can have very different performance characteristics.

Depending on their hydraulic design, one may be intended for higher flow at lower head while another may be designed to produce lower flow at significantly greater head.

So instead of starting with:

“What horsepower do I need?”

start with:

“How many GPM do I need at my required total dynamic head?”

Then determine which pump and motor combination meets those requirements.

6. Choose the Correct Voltage

Residential submersible well pumps are commonly available in different electrical configurations.

The replacement pump generally needs to match the electrical system available at the installation.

You'll commonly encounter 115V and 230V equipment, although availability depends on pump size, motor, manufacturer, and application.

Larger motors are commonly 230V.

If you're replacing an existing pump, don't assume the voltage based solely on horsepower. Verify the existing electrical supply and motor specifications.

Electrical work should be performed in accordance with applicable electrical codes and manufacturer requirements.

7. Understand 2-Wire vs. 3-Wire Motors

This terminology confuses a lot of people.

A 2-wire submersible motor typically contains its starting components within the motor.

A 3-wire submersible motor uses an above-ground control box containing starting components.

And yes—the terminology can be confusing because the equipment grounding conductor isn't included in the “2-wire” or “3-wire” naming convention.

Neither configuration is automatically the right choice for every installation.

If you're replacing an existing pump, knowing whether your current system uses a control box is an important clue.

We'll cover this topic in more detail in our upcoming guide:

2-Wire vs. 3-Wire Submersible Well Pumps: What's the Difference?

8. Make Sure the Pump Fits the Well

Most residential submersible pumps are designed for a particular minimum well diameter.

For example, many common residential submersible pumps are designed for use in 4-inch or larger wells, but requirements vary by manufacturer and model.

Never assume that a pump will fit simply because it's described as a “4-inch pump.”

Check the manufacturer's actual dimensional and installation requirements.

What Information Should You Have Before Buying?

Before shopping for a replacement or new well pump, try to gather:

• Well depth
• Static water level
• Pumping water level, if available
• Well recovery/yield rate
• Desired flow rate (GPM)
• Desired system pressure
• Voltage
• Existing pump model, if replacing one
• Motor horsepower
• 2-wire or 3-wire configuration
• Well casing diameter
• Pipe size
• Distance from the well to the pressure tank/home
• Any significant elevation changes

Don't have every number?

That's okay.

Some information may be available on your well completion report, existing equipment labels, or documentation from the original installation.

Replacing an Existing Well Pump?

If your existing system performed well before the pump failed, the old pump's model number can be extremely useful.

But don't automatically replace it with something based only on matching horsepower.

Changes to the well, water level, household demand, or the original system design can affect whether the same pump is still the appropriate choice.

Whenever possible, compare the replacement pump's performance curve with the requirements of the system.

The Bottom Line

Choosing the right submersible well pump comes down to matching your water demand with your well and system conditions.

Instead of asking only:

“What horsepower pump do I need?”

think in terms of:

How much water do I need?
How far does the pump need to move it?
At what pressure?

Once you know those things, selecting the right pump becomes much easier.

Still Not Sure Which Pump You Need?

You don't have to figure it out alone.

The Water Pumps Pro team works with pumps and water systems every day. If you have your well information or the model number of your existing pump, we can help you narrow down your options