Pump TDH Input Form
Example Data Table
| Scenario | Flow GPM | Pipe Length ft | Pipe Size in | Static Head ft | Outlet psi | Typical Use |
|---|---|---|---|---|---|---|
| Small site transfer | 120 | 180 | 3 | 35 | 15 | Trench water removal |
| Medium dewatering | 250 | 300 | 4 | 53 | 25 | Foundation pumping |
| High flow bypass | 600 | 500 | 6 | 75 | 30 | Temporary bypass line |
Formula Used
TDH = Static Head + Pressure Head + Friction Head + Minor Loss Head + Velocity Head
Pressure Head = PSI × 2.31 ÷ Specific Gravity
Friction Head = 4.52 × L × Q1.85 ÷ C1.85 × d4.87
Velocity Head = V2 ÷ 2g
Brake HP = GPM × TDH × Specific Gravity ÷ 3960 ÷ Efficiency
Static head covers vertical lift. Pressure head converts required discharge pressure into feet of liquid. Friction head estimates pipe resistance using the Hazen-Williams method for water service. Minor losses estimate fittings, valves, bends, strainers, and entrance losses. Velocity head accounts for moving liquid energy at the discharge.
How to Use This Calculator
Enter the required flow rate first. Add the pipe length, inside diameter, and roughness coefficient. Then enter the vertical suction and discharge heads. Add the required outlet pressure. Include a combined minor loss K value for fittings and valves. Enter the specific gravity of the liquid. Add a safety margin to protect the design from field variation. Press the calculate button. The result appears above the form, directly below the header section.
Construction Pump TDH Planning Guide
Why Total Dynamic Head Matters
Total dynamic head is one of the most important values in pump selection. It shows the total resistance a pump must overcome while moving water or another liquid. On construction sites, this number affects pump size, power demand, discharge pressure, fuel use, and reliability. A low estimate can cause weak flow, slow dewatering, cavitation, or motor overload. A high estimate can lead to oversized equipment and wasteful operating cost.
What This Tool Checks
This calculator combines elevation, pressure, pipe friction, fitting losses, and velocity head. It also adds a safety margin for uncertain site conditions. The pipe friction estimate uses the Hazen-Williams equation, which is common for water movement. The tool also estimates water horsepower and brake horsepower. These values help compare pump duty points with manufacturer curves.
Using Field Values
Good field data improves the result. Measure vertical lift from the water source to the pump centerline. Measure discharge height from the pump to the final outlet point. Use the actual inside pipe diameter, not only the nominal pipe size. Add extra equivalent length for long hoses, sharp bends, check valves, strainers, and fittings. Rough hoses and older pipes can need a lower Hazen-Williams coefficient.
Practical Design Advice
Review the final TDH beside the needed flow rate. Then check a pump curve at that operating point. Avoid choosing a pump only by horsepower or outlet size. The pump must deliver the target flow at the calculated head. Also check suction conditions. Poor suction layout may reduce available net positive suction head. Keep suction pipe short, straight, sealed, and properly submerged. For critical construction pumping, confirm results with site measurements and supplier data.
FAQs
What does TDH mean for a pump?
TDH means total dynamic head. It is the full head a pump must overcome, including static lift, pressure demand, pipe friction, fittings, and velocity head.
Is static head the same as total dynamic head?
No. Static head is only elevation difference. Total dynamic head also includes pressure head, friction losses, minor losses, and velocity effects.
Which pipe friction method is used here?
This calculator uses the Hazen-Williams equation. It is commonly used for water flow in construction, irrigation, plumbing, and temporary pumping lines.
Can I enter a flooded suction condition?
Yes. Enter static suction as a negative value when liquid level is above the pump centerline. This reduces the static head requirement.
Why is outlet pressure converted to feet?
Pump head is commonly compared in feet. Pressure in psi is converted to feet using 2.31 divided by specific gravity.
What is a good safety margin?
Many site estimates use 5% to 15%. Use a higher margin when pipe routing, fittings, or elevation data are uncertain.
Does this replace a pump curve?
No. Use the result to find the required duty point. Then compare that flow and head against the manufacturer pump curve.
Why is NPSHa included?
NPSHa helps review suction risk. Low available suction head can cause cavitation, vibration, performance loss, and pump damage.