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Size water supply pipes by fixture units and flow rate. Calculate copper and PEX pipe diameter for residential plumbing per IPC fixture unit tables.
Calculate water flow rate GPM from pipe velocity and diameter. Size pipes and estimate fixture supply capacity for plumbing and irrigation design.
Calculate drain pipe slope per IPC code. Enter pipe diameter and run length to get minimum and recommended fall in inches per foot for waste lines.
Q in GPM, L in feet, D in inches, C is pipe roughness coefficient (copper C≈130, PVC C≈150).
Head Loss = 4.52 × Q^1.852 × L ÷ (C^1.852 × D^4.871)Convert feet of head to PSI. Elevation gain also adds 0.433 PSI per foot of vertical rise.
PSI = Head (ft) × 0.433Fixtures typically need 20–80 PSI. Below 20 PSI causes poor performance; above 80 may need PRV.
Fixture PSI = Source PSI − Friction Loss − Elevation LossUpdated: July 2026
Rural supply line may lose 15–25 PSI friction. Upsize to 1″ if fixture pressure below 30 PSI at peak flow.
Elevation loss ≈ 5.2 PSI plus friction. Boost pressure or increase main pressure if shower flow weak.
Calculate drop on lateral to ensure sprinkler heads operate at manufacturer PSI range (typically 30–50 PSI).
Estimate pressure loss in water pipes due to friction and elevation change. Enter flow rate, pipe diameter, length, and material to calculate PSI drop between source and fixture — essential for multi-story homes and long rural supply lines.