A water pump listing may include horsepower, gallons per hour, gallons per minute, and maximum head height. These numbers describe different aspects of performance, and comparing just one of them can lead to the wrong choice.
The most important question is not simply, “Which pump has the highest GPH?” It is, “How much water can this pump move through my actual installation?”
This guide explains the main specifications and how to read them together.
What Does GPH Mean?
GPH stands for gallons per hour. It describes a volume of water moved over one hour under specified operating conditions.
For example, 2,400 GPH is equivalent to 40 gallons per minute. That is a unit conversion, not a guarantee that the pump will deliver that flow through every hose or at every height.
Check whether a product specification refers to US gallons or another gallon standard. The examples in this guide use US gallons.
What Does GPM Mean?
GPM stands for gallons per minute. It measures the same type of performance as GPH, but over a shorter period.
To convert between them:
GPM = GPH ÷ 60
GPH = GPM × 60
For example, 1,800 GPH equals 30 GPM, while 3,000 GPH equals 50 GPM.
Always convert flow rates to the same unit before comparing pumps. A larger-looking number may simply reflect a different unit.
What Is Head Height?
Head describes the energy a pump adds to water, expressed as an equivalent height of water.
For many drainage applications, the easiest starting point is vertical lift: the elevation difference between the source water surface and the discharge destination.
However, vertical lift is not the whole requirement. The pump also needs to overcome resistance through hoses, pipes, fittings, and valves. If the destination requires pressure, that requirement must also be included.
Together, these factors determine the system’s total dynamic head at a particular flow rate.
Maximum Flow and Maximum Head Are Not Simultaneous
This is one of the most important distinctions in a pump listing.
Maximum flow is generally measured at low head under the manufacturer’s test conditions. Maximum head is typically the point where delivered flow approaches zero.
A pump advertised with a maximum flow of 3,000 GPH and a maximum head of 25 feet should not be expected to deliver 3,000 GPH at a height of 25 feet.
Those figures describe different ends of its performance range. To understand what happens between them, look for a performance curve or flow-at-head table.
The numbers above are illustrative, not specifications for a particular FOTING model.
How to Read a Pump Performance Curve
A typical performance curve shows flow rate on the horizontal axis and head on the vertical axis.
For a stated head requirement, find the corresponding point on the curve and read the approximate flow. Alternatively, start with the flow you need and check how much head the pump can provide at that flow.
Use the curve for the exact model and operating configuration. Similar-looking pumps, or pumps with the same horsepower, can have different curves.
If the manufacturer provides only maximum figures, ask for flow data at your expected installation conditions before making a critical sizing decision.
Why Hose Length and Diameter Matter
A hose can reduce delivered flow even when the discharge point is not much higher than the water source.
Longer runs, narrow inside diameters, sharp bends, and restrictive fittings all add resistance. Friction losses also increase as flow increases.
A horizontal hose does not add elevation simply because it is long, but it still contributes friction loss. There is no universal rule that converts every foot of horizontal hose into a fixed amount of vertical lift.
For hose sizing and connection checks, see our companion article, How to Choose a Discharge Hose for Your Submersible Pump.
Is a Higher-Horsepower Pump Always Better?
No. Horsepower describes power, not the complete performance of the installation.
Impeller design, pump efficiency, motor characteristics, and the discharge system all affect the result. A higher-horsepower pump is not automatically the best fit for a small or restrictive drainage setup.
Compare the required flow at the expected head, then check electrical requirements, permitted water type, control method, and operating limits.
Estimating Drainage Time
If you know the usable water volume and the actual delivered flow, you can make a rough estimate:
Drainage time in hours = water volume in gallons ÷ delivered flow in GPH
For example, removing 600 gallons at an actual delivered flow of 1,200 GPH would take approximately half an hour.
This example assumes no additional water is entering and the flow remains constant. In practice, changing water levels, continuing inflow, and minimum operating water levels can change the result.
Do not use the advertised maximum flow as the delivered flow unless it matches your installation conditions.
Different Pump Types Need Different Comparisons
A submersible drainage pump, a shallow well jet pump, and a pool circulation pump do not perform interchangeable jobs.
For a drainage pump, consider the volume to remove, lift, discharge route, and permitted debris size.
For a shallow well jet pump, also evaluate suction conditions, priming requirements, and required delivery pressure.
For a pool pump, evaluate the pool system’s flow requirements and the limitations of the filter, plumbing, and other equipment.
A pressure washer is another distinct application. A high PSI rating does not make it a substitute for a drainage pump.
What to Check Before Ordering a FOTING Pump
Before comparing models, write down the job the pump needs to perform, the water type, the required flow, the approximate elevation difference, and the proposed hose or pipe route.
Then review the individual model’s performance information, discharge connection, electrical requirements, and control type.
If the application involves permanent plumbing, a pressurized system, or uncertain sizing, get qualified help rather than selecting by maximum GPH alone.
Final Takeaway
GPH and GPM describe flow. Head describes the energy needed to move water through the system. Horsepower alone does not tell you how those factors will work together.
Choose a pump based on the flow it can deliver at your expected operating conditions, not simply the largest number in the product title.
If you need help comparing FOTING pumps, contact JUNHE PUMPS with your application, approximate lift, and hose or pipe details.