Pipe Network Pressure Drop Solver

What this solver does

Most online calculators size a single pipe. Real systems are networks: a chilled-water loop has a supply main, branch runs to each air handler, riser lifts, dozens of fittings, and a return path — and the pump must overcome the sum of all their losses along the worst-case (index) circuit. This tool adds up the pressure drop of every segment you enter and returns the total dynamic head the pump must deliver.

The method

Each segment's friction loss is computed with the Darcy-Weisbach equation, h_f = f · (L/D) · V²/2g, where the friction factor f comes from the Swamee-Jain approximation of the Colebrook equation using the pipe's relative roughness and Reynolds number. Fitting losses use the velocity-head method (h = K · V²/2g), and elevation change adds static head. For a closed loop the net elevation cancels (every foot up is a foot back down), so the pump only fights friction and fittings; for an open system the net static lift is added.

How to use it

• Enter each pipe run of your index circuit as a segment: flow (GPM), nominal size, length, elbow count, any extra fitting K, and elevation change.
• Pick the material (sets roughness) and whether the system is a closed loop or open.
• Solve — you get per-segment velocity and loss, plus the total pump head in feet and psi.
• Watch the velocity warnings: keep water velocity roughly under 8 ft/s to avoid noise and erosion, and friction rate near 1–4 ft per 100 ft for efficient design.

Pair it with the single-line pump head calculator, the chilled water pipe sizing calculator, and the pipe sizing calculator. This tool gives a reliable engineering estimate of system head; a final design should be confirmed by a licensed engineer against the manufacturer's fitting data and pump curves.