1/2 hp vs 3/4 hp Submersible Well Pump: How to Choose What’s Right for You

For homeowners who rely on a private well for their water supply, having a reliable submersible well pump is critical. Submersible pumps are located down inside the actual well casing, underwater beneath the water table. This type of pump is quiet, efficient, and suitable for use in wells up to several hundred feet deep.

When it comes time to purchase a new well pump, one of the most important decisions is pump horsepower. The two most common sizes for residential use are 1/2 hp and 3/4 hp submersible pumps. But which is better for your well – the smaller 1/2 hp or the more powerful 3/4 hp model?

In this guide, we’ll provide an in-depth look at key differences between 1/2 and 3/4 hp submersible pumps. We’ll cover performance specs, recommended usage, costs, lifespan, maintenance needs, and other factors to help you choose the right pump horsepower for your water supply requirements.

Here is an in-depth comparison table contrasting 1/2 hp and 3/4 hp submersible well pumps:

What is a Submersible Well Pump?

Before diving into the details on pump motor sizes, it helps to understand exactly what a submersible pump is and how it works.

Definition

A submersible well pump is a type of centrifugal pump designed to be installed below ground level inside the well casing, submerged below the water line. These pumps utilize an electric motor that powers the impellers to lift water to the surface.

Components

Submersible pumps consist of:

• Pump Housing – Sealed watertight chamber that contains the impellers and motor
• Impellers – Rotating discs that generate suction to lift water
• Motor – Powers the impellers; sized in horsepower (hp)
• Drive Shaft – Connects impellers to motor
• Bearings – Allow shaft to spin smoothly
• Inlet Screen – Prevents sediment from entering pump
• Discharge Pipe – Carries water to the surface
• Power Cable – Connects motor to power source

How It Works

The electric motor turns the drive shaft and impellers within the submerged pump housing. The spinning impellers generate suction that draws water in through the inlet. The water passes through the impellers and is pushed up the discharge pipe to the well head. These pumps provide high lift capacities of up to 400 feet or more.

Now that we’ve covered the basics of what a submersible pump is, let’s look at how to determine the right size based on your well’s specifications.

Key Factors to Consider When Choosing a Pump

Choosing the optimum horsepower size depends primarily on two key factors:

Well Depth and Flow Rate Needs

• Well depth – The vertical distance in feet from the ground surface down to the static water level determines how much lifting capacity the pump requires. Deeper wells need more horsepower.
• Flow rate – The volume of water in gallons per minute (gpm) the pump must supply to meet household water demand. Higher flow calls for more horsepower.

You’ll need to match a pump that can produce the desired flow rate from the total lift distance from well depth.

Power Requirements

• The pump motor runs on single phase 220-240V power in most residential applications.
• 1/2 hp models commonly draw around 5-7 amps.
• 3/4 hp uses around 7-10 amps.

Your electrical panel must have sufficient capacity to handle the motor’s starting and running amp load.

Now that we’ve covered the basic criteria, let’s compare 1/2 and 3/4 hp submersible pumps…

1/2 HP vs 3/4 HP Submersible Pumps

We’ll look at common pump models, specifications, performance differences, and recommendations for usage of the two motor sizes.

Common Models and Specs

1/2 hp:

• Flow rates: 4 – 15 gpm
• Total heads: 100 – 180 feet
• Motor power: 1/2 hp
• Voltage: 220-240V
• Amps: around 5 – 7A

Example models: Sta-Rite 6P5R, Wayne S50N1-7

3/4 hp:

• Flow rates: 10 – 25 gpm
• Total heads: 130 – 400+ feet
• Motor power: 3/4 hp
• Voltage: 220-240V
• Amps: around 7 – 10A

Example models: Sta-Rite 8P75R, Goulds JS43S6EME75

As you can see, 3/4 hp pumps offer higher flow rates and total heads. They can lift water from greater depths with higher output.

Performance Differences

The main differences boil down to:

• Flow rate – 3/4 hp allows up to 25 gpm vs 15 gpm for 1/2 hp
• Total head – 3/4 hp pumps up to 400+ feet, while 1/2 hp maxes out around 180 feet
• Power – More horsepower enables higher pumping capacities

So the 3/4 hp has a performance edge for deeper wells and higher water demand. But that doesn’t mean 1/2 hp can’t be adequate for shallower, lower-yield wells.

Usage Recommendations

When to choose 1/2 hp:

• Well depth 100 feet or less
• Flow rate demand up to about 10 gpm
• Smaller households with lower water needs

When to choose 3/4 hp:

• Well depth over 100 feet
• Flow rates over 10 gpm
• Larger households with higher demand

As a rule of thumb, 3/4 hp allows for extra power, flow rate, and head capacity, while 1/2 hp may suffice for shallower wells with lighter demands.

Next let’s compare costs…

This covers the key differences between 1/2 and 3/4 hp submersible well pumps in terms of typical specs, performance capabilities, and recommended usage. In the next section, we’ll look at how upfront costs, operating costs, lifespan, and maintenance needs factor into the decision.

Cost Comparisons

When selecting a well pump, it’s not just about pump performance – cost is often a major factor as well. Let’s look at how 1/2 hp and 3/4 hp submersible pumps compare in terms of upfront costs, operating costs, lifespan, and maintenance needs.

Upfront Costs

The purchase price is typically 15-30% higher for a 3/4 hp pump compared to a comparable 1/2 hp model. For example:

• Sta-Rite 6P5R (1/2 hp) – $250
• Sta-Rite 8P75R (3/4 hp) – $325

So you’ll usually pay more upfront for the extra power of a 3/4 hp pump. This should be weighed against the higher performance you’re gaining.

Operating Costs

Since 3/4 hp motors draw more amps, they will cost a bit more to run on an ongoing basis. Exact energy use will depend on run time.

For example, running a 1/2 hp pump 6 hours a day at $0.15 per kWh would cost around $4.50 per month. A comparable 3/4 hp model may use around $5.25 in electricity monthly with the same run time.

So energy costs average 15-25% higher for 3/4 hp pumps compared to 1/2 hp units of similar make and flow rate. This equates to $90 more per year for the 3/4 hp pump in our example.

Lifespan and Maintenance

1/2 hp and 3/4 hp submersible pumps generally have a comparable lifespan when sized properly and maintained well. Properly installed, either should last 10-15 years or more before needing replacement.

Ongoing maintenance costs are similar – changing lubricants yearly, replacing wear parts as needed, occasional motor repairs if issues arise. Overall maintenance costs average $200-300 annually for parts, lubricants and periodic service.

So in terms of longevity and maintenance, there is not a significant difference between 1/2 and 3/4 hp models. Selecting the right size for your well’s output and lifting needs is more important. An oversized unit will wear out faster.

To summarize:

• 3/4 hp costs more upfront
• 3/4 hp costs a bit more in yearly energy to run
• Properly sized units have similar lifespans and maintenance needs

Now let’s look at a few other factors to weigh…

Other Considerations

Beyond performance, costs and sizing, here are a few other things to think about when choosing between 1/2 and 3/4 hp pumps:

Water Quality

Higher flow rates enabled by more powerful 3/4 hp pumps can help reduce sediment buildup. The faster water velocity flushes sand and particles out of the well. This may provide cleaner water, especially in wells that experience heavier sediment.

Well Size and Construction

Make sure the pump matches the well diameter – 4″ minimum for 1/2 hp and 5″ for 3/4 hp. Also consider well depth and output capacity based on flow tests. A 3/4 hp pump won’t reach full potential in an under-producing well.

Above-Ground Piping

Larger 3/4 hp units require piping sized for higher flow rates – 1″ diameter or greater. Make sure your plumbing can handle a more powerful pump.

Control & Pressure Tanks

Matching well pump output to storage and pressure tanks is key. Oversized pumps increase pressure tank cycling and wear. Bigger pumps may also necessitate upsizing your pressure tank.

So in summary – the 3/4 hp allows for higher flow that can benefit water quality, but only if the well yield and plumbing can support it. Make sure to size your pump for your specific system.

FAQs

How much flow rate do I really need from my well pump?

Look at your peak usage and storage capacity. Total the GPM ratings of fixtures/appliances used simultaneously to determine needed flow. Add some buffer too.

What size piping should I use with my new pump?

1/2 hp pumps usually require 3/4″ or 1″ piping. 3/4 hp works best with 1″ or larger pipe diameters to avoid restrictions.

Can I install a 3/4 hp pump in a 4″ well casing?

Not recommended. 5″ diameter or larger well casing is best for 3/4 hp pumps. Always match pump size to well bore.

How often will a 1/2 hp pump cycle on and off?

Depends on usage, storage tank size, and pressure settings – but expect 6-10 cycles per hour during peak demand times.

Should I upgrade my pressure tank when replacing my pump?

It’s wise to review pressure tank capacity when upsizing pumps. Bigger units may necessitate a larger tank. Check pre-charge levels too.

Conclusion

Choosing between a 1/2 hp or 3/4 hp submersible well pump ultimately depends on your well’s production capability and your household water requirements.

For shallower wells under 100 feet deep and lower demand under 10 gpm, a 1/2 hp model may be the optimal fit. It provides adequate power at a lower upfront and operating cost.

For deeper wells over 100 feet and higher flow rates needed, a 3/4 hp unit is likely the better choice. The extra horsepower enables greater pumping capacity for higher demand, despite somewhat higher purchase price and energy use.

Be sure to match pump performance to your well’s output capability, storage capacity, and plumbing size. Oversizing decreases efficiency. Understand your usage needs, well depths and flows to pick the right pump horsepower.

With the information in this guide, you can make an informed decision between 1/2 and 3/4 hp well pumps based on performance requirements, costs, and other factors – choosing the best fit for your residential water supply needs.