Calculator Inputs
Formula Used
- Flow conversion: converts your input to Q in m³/s.
- Required diameter: D = √( 4Q / (π·V_design) ) where V_design = V_max / SafetyFactor.
- Velocity check: V_actual = Q / A, with A = π·D²/4.
- Head loss (valve + strainer): h = K_total · V_actual² / (2g), where K_total = K_valve + K_strainer.
- Total suction head (estimate): H ≈ StaticLift + h (does not include pipe friction).
How to Use This Calculator
- Enter your target flow rate and select units.
- Set a max suction velocity; lower improves priming stability.
- Choose valve type and strainer screen, or enter custom K values.
- Add static suction lift to estimate suction-side head demand.
- Press calculate and review recommended size and advisory.
- Download CSV or PDF to share with your installer.
Example Data Table
| Flow (L/min) | Max V (m/s) | Safety | Valve | Screen | Recommended Size (mm) | Velocity (m/s) | Head Loss (m) |
|---|---|---|---|---|---|---|---|
| 25 | 1.4 | 1.10 | Swing | Medium | 25 | 0.85 | 0.18 |
| 40 | 1.5 | 1.15 | Swing | Medium | 32 | 0.83 | 0.17 |
| 65 | 1.6 | 1.20 | Poppet | Fine | 40 | 0.86 | 0.30 |
| 95 | 1.8 | 1.25 | Spring | Medium | 50 | 0.81 | 0.35 |
Sizing for Stable Suction and Priming
Foot valves protect garden pumps by holding prime and blocking backflow. A correctly sized valve keeps suction velocity moderate, reducing air entrainment, vibration, and cavitation risk. Use this calculator to align valve diameter with your target flow and a conservative velocity, then apply a safety factor when water contains bubbles, long suction runs, or starts.
Balancing Velocity, Head Loss, and Flow Demand
Flow determines the minimum opening area needed. The calculator uses continuity to compute a required diameter and then checks actual velocity for the nearest standard size. Many installers aim for 1.0–1.8 m/s on suction lines. It also estimates minor-loss head from valve and strainer K values. Lower velocity means lower losses, better priming stability, and operation.
Strainer Selection for Clean Water Intake
Strainers prevent leaves, sand, and algae from reaching the pump. Fine screens offer better protection but increase resistance and clogging likelihood, which raises suction head over time. For ponds or canals, select a screen that matches debris conditions and schedule cleaning intervals. When you know a manufacturer’s loss data, enter custom K values for more accurate results and compare alternative screen areas.
Practical Installation Guidelines
Place the foot valve below the lowest expected water level and keep it off the bottom to avoid silt ingestion. Use a rigid suction line where possible, minimize elbows, and seal joints to prevent air leaks. Support the line to reduce strain on fittings. Add a union or quick coupling for maintenance. After installation, verify that prime holds overnight and recheck after the first cleaning.
Using Reports for Planning and Maintenance
Download the CSV or PDF report to document assumptions, standard size selection, and suction-head estimates. Share it with installers when you upgrade pumps, change water sources, or add extra irrigation zones. Recalculate after seasonal changes, because warmer water, clogged screens, and higher lift can reduce suction performance. If pipe friction is significant, add it to the estimate before final sizing.
FAQs
1) What suction velocity should I target?
For most small irrigation systems, 1.0–1.8 m/s is a practical range. Lower velocities improve priming stability and reduce the chance of air leaks showing up as bubbles. Use the safety factor to stay conservative.
2) Why is a safety factor included?
It reduces the design velocity so the recommended nominal size is larger. This helps when screens foul, water has entrained air, or the pump cycles often. A modest factor like 1.10–1.25 is common for garden sources.
3) Should the foot valve match the suction pipe size?
Usually, match the valve nominal size to the suction line to avoid sudden contractions. If the calculator recommends a larger size, upsize the valve and the intake section, or use gradual reducers to keep velocity smooth.
4) How do I pick the strainer screen option?
Choose coarse for cleaner wells, medium for typical tanks, and fine for light sand or algae risk. Fine screens protect better but clog sooner. Cleanable area matters; larger screen surface reduces head loss at the same flow.
5) Does the result include pipe friction losses?
No. The head loss shown is for the foot valve and strainer only. Long suction lines, small pipe diameters, and many fittings can add significant friction. Add a separate friction estimate before finalizing pump selection.
6) When should I recalculate sizing?
Recalculate after changing pumps, adding irrigation zones, altering lift height, or switching water sources. Also rerun if the system loses prime, the strainer clogs frequently, or seasonal debris increases. Small adjustments can improve reliability.