Project-stage HGL checks
Hydraulic grade line evaluation is a fast screening tool for buried and exposed pipe runs. By combining elevation with pressure head, the line reveals whether a segment maintains positive pressure, protects against intrusion, and supports required service levels. Early checks help confirm pump selection, reservoir set points, and workable tie-in elevations before drawings are issued. For phased work, run separate cases for peak demand, flushing, and commissioning to avoid surprises during testing and turnover at each milestone.
Field inputs that matter
Reliable results depend on consistent upstream pressure readings, surveyed elevations, and a realistic flow estimate for the operating scenario. Diameter and length should reflect the hydraulic path, not just plan distance. Minor losses should include entrances, valves, bends, and reducers. When fittings vary, using a conservative total K value provides a safer margin for construction decisions.
Interpreting losses and slopes
The calculator reports major loss from wall friction and minor loss from localized disturbances. A steep HGL drop often signals high velocity, undersized pipe, or excessive fittings. If the end hydraulic grade line falls below the pipe centerline, end pressure can become negative. That condition can promote cavitation risk and contamination pathways in intermittent systems. When results look marginal, consider increasing diameter, trimming fittings, or adjusting upstream setpoint, then rerun to quantify improvement before issuing shop drawings.
Friction factor selection
You may enter a friction factor from standards or compute it using roughness and viscosity. For turbulent flow, the computed option approximates common chart behavior and adapts to rougher pipe. For laminar regimes, the factor follows 64/Re automatically. Matching the factor approach to material age and lining condition improves defensible design documentation.
Deliverables for submittals
Use the results table to document assumptions, calculated velocity, and total head loss. Include both hydraulic and energy grade lines when communicating with mechanical and civil teams. Exporting CSV supports traceability across multiple alignment segments, while PDF output provides a clean attachment for QA packages, method statements, and client review cycles.
FAQs
Use it to see pressure head plus elevation along a pipeline. It helps confirm positive pressure, identify low points, and check if downstream pressure meets operational needs.
The calculator converts upstream pressure to head, subtracts major and minor head losses, then converts the remaining pressure head at the end back to kPa using density and gravity.
Use it when you know pipe roughness and fluid viscosity, or when conditions may change with temperature or aging. It adapts friction based on Reynolds number and relative roughness.
Negative pressure occurs if elevation rise and head losses exceed available upstream head. This often indicates high flow, undersized diameter, long runs, or excessive fittings.
Add K values for each fitting, valve, entrance, and exit in the segment. If unsure, use conservative totals from standards or vendor data to avoid underestimating losses.
No. It is best for single-run checks or quick sensitivity studies. For complex loops, varying demands, pumps, and control valves, use a dedicated network solver and calibrated field data.