Free tool
Total Dynamic Head & Design Flow Rate
Size a septic or effluent pump: design flow rate from your orifice layout, and total dynamic head from static lift and system losses.
Step 1
Design Flow Rate
Flow rate is the number of orifices in the distribution laterals multiplied by the discharge rate per orifice.
0.43 gpm is the common default for 1/8″ orifices at 5 ft of residual head.
Design flow rate (N × R)
0.00 gpm
Step 2
Total Dynamic Head (TDH)
TDH is the sum of every head the pump must overcome, in feet.
Total dynamic head (A+B+C+D+E)
0.00 ft
These equations cover level sites where all lateral pipes sit at the same elevation. For sloped or more complex sites, consult a professional to ensure even distribution throughout the system.
SiteFacts
Email me this sizing worksheet
We’ll send your flow rate and TDH numbers, and can tell you what the county publishes about septic feasibility for a specific parcel.
What each input means
Static head (A)
Vertical distance from the pump-off level in the tank to the highest point in the distribution system.
Friction head (B)
Head lost to friction in the transport pipe and fittings — depends on pipe size, length, and flow rate.
Discharge assembly (C)
Losses through the check valve, unions, and fittings at the pump discharge.
System allowance (D)
Residual head required at the laterals so every orifice discharges evenly — commonly 5 ft.
Sizing a pump for land you don’t own yet?
Pump sizing assumes the lot can support a septic system at all. A SiteScore screens septic feasibility — soils, setbacks, and what the county already knows about the parcel — before you spend on design.