Sizing Result
Advanced Well Pump Inputs
Example Data Table
| Use Case | Flow | Pumping Level | Pressure | Estimated TDH | Typical Pump Range |
|---|---|---|---|---|---|
| Small cabin | 6 GPM | 70 ft | 40 PSI | 165 ft | 0.5 HP |
| Average home | 10 GPM | 110 ft | 50 PSI | 250 ft | 0.75 to 1 HP |
| Large home | 15 GPM | 160 ft | 60 PSI | 340 ft | 1.5 to 2 HP |
| Irrigation support | 25 GPM | 140 ft | 55 PSI | 330 ft | 2 to 3 HP |
Formula Used
The calculator estimates total dynamic head before selecting pump horsepower.
Pumping Level = Static Water Level + Drawdown
Pressure Head = PSI × 2.31
Friction Loss = 4.52 × Q^1.85 × L ÷ (C^1.85 × D^4.87)
TDH = Pumping Level + Elevation Gain + Pressure Head + Friction Loss
Adjusted TDH = TDH × (1 + Safety Margin ÷ 100)
Water HP = GPM × Adjusted TDH ÷ 3960
Brake HP = Water HP ÷ Pump Efficiency
This method gives a planning estimate. Final pump selection should use the pump curve from the manufacturer.
How To Use This Calculator
Enter your required flow in gallons per minute. Use the total fixture demand or irrigation demand. Add static water level, drawdown, elevation gain, pressure, pipe length, fitting allowance, pipe diameter, and efficiency. Press the calculate button. The result appears above the form and below the header. Review total head, horsepower, recommended pump size, and daily capacity.
Well Pump Sizing Guide
Why Pump Size Matters
A well pump must move water from the well to the pressure system. It must also overcome depth, pipe friction, elevation, and desired outlet pressure. A weak pump may run too long. It may fail to satisfy peak demand. An oversized pump can short cycle. That can damage motors, pressure switches, and tanks.
Flow Rate Planning
Flow rate is the first sizing point. Homes usually need enough flow for fixtures used at the same time. Irrigation systems often need higher flow. Use a realistic peak demand. Do not size only from daily gallons. A low flow pump may still fill a tank slowly. Yet it may not support showers, appliances, and hose use together.
Total Dynamic Head
Total dynamic head is the main pressure burden. It includes pumping water level, elevation gain, pressure head, and pipe friction. Pressure head converts PSI into feet of water. One PSI equals about 2.31 feet of head. Friction grows quickly as flow rises. Small pipes can add large losses.
Efficiency And Horsepower
Water horsepower shows the ideal hydraulic power. Real pumps need more power because motors and impellers are not perfect. Efficiency adjusts this gap. A safety margin adds reserve for aging, small data errors, and seasonal changes. The calculator rounds the result toward standard pump horsepower sizes.
Pump Curve Check
Always compare the final result with a pump curve. Choose a pump that delivers your target GPM at your calculated head. The best point should be near the efficient operating range. Avoid selecting only by horsepower. Two pumps with the same horsepower can have very different flow and head performance.
FAQs
1. What is total dynamic head?
Total dynamic head is the full lift and pressure burden on the pump. It includes pumping level, elevation gain, pressure head, and friction loss.
2. Why is drawdown important?
Drawdown shows how far water falls while pumping. It increases the working lift. Ignoring it can make the pump too small.
3. How much pressure should I enter?
Most homes use 40 to 60 PSI. Enter the pressure you want at the tank or service point after the pump runs.
4. Does pipe size affect pump sizing?
Yes. Smaller pipe raises friction loss. This increases total head and may require a stronger pump or lower flow target.
5. What is a good safety margin?
A 10 percent margin is common for planning. Use more if measurements are uncertain, pipe runs are complex, or the well changes seasonally.
6. Can horsepower alone select a pump?
No. Horsepower is only one part. The pump curve must confirm the pump can deliver your GPM at the calculated head.
7. What efficiency value should I use?
Small well systems often range from 45 to 65 percent overall efficiency. Use the manufacturer value when available.
8. Is this calculator suitable for irrigation?
Yes, for planning. Enter irrigation flow and pressure needs. Verify the result against zone demand and a manufacturer pump curve.