Mainline Fill Time Calculator

Know how fast your irrigation mainline charges up. See volume, flow, and time instantly clear. Adjust diameter and velocity to avoid surges safely always.

Calculator
Choose a known flow rate or estimate flow using a target velocity.
Flow is split across parallel lines.
Total pipe length being filled.
Use true inside diameter, not nominal.
If 3 mains fill together, enter 3.
%
Use <100% for partial priming or staged fill.
%
Typical 3–10% for air release and fittings.
Enter combined flow feeding all parallel lines.
Applies to result flow values.
Reset
Example Data Table
Sample scenarios to help validate your inputs.
Length Inside Diameter Parallel Lines Method Flow / Velocity Fill % Safety % Estimated Fill Time
60 m 32 mm 1 Known flow 120 L/min 100% 5% ≈ 0.74 min
200 ft 1.5 in 2 Known flow 60 gpm (total) 100% 8% ≈ 1.20 min
120 m 50 mm 1 Target velocity 1.0 m/s 80% 5% ≈ 1.32 min
Actual times vary with valves, air release, and control strategy.
Formula Used
Core relationships used in this calculator.
1) Pipe Volume
Area (A) = π × D² ÷ 4
Volume (V) = A × L
D is inside diameter, L is length.
2) Effective Volume
Vₑ = V × (Fill% ÷ 100) × (1 + Safety% ÷ 100)
Safety% captures air release, fittings, and startup uncertainty.
3) Flow and Fill Time
If flow is known: Time (t) = Vₑ ÷ Q
If using velocity: Q = A × v
When filling multiple lines together, total flow is split equally.
How to Use This Calculator
Steps to get reliable startup timing.
  1. Measure the mainline length you want to fill and choose units.
  2. Use inside diameter from pipe data sheets or calipers.
  3. Select a method: enter a known supply flow, or pick a target velocity.
  4. Set fill percentage if you stage filling in steps.
  5. Add a safety factor to cover air and fittings volume.
  6. Click Calculate, then download CSV or PDF if needed.

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Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.