Design suction lines for pumps and filters. Compare materials, fittings, and temperatures before purchasing parts. Get safe diameters, low losses, and quieter watering sessions.
Enter your suction-side conditions. For best results, keep suction velocity low and the lift minimal.
Typical small-garden pumping setup. Your project may differ.
| Flow | Suction length | Lift | Temp | Material | Fittings | Target velocity | Expected output |
|---|---|---|---|---|---|---|---|
| 2.0 m³/h | 8 m | 1.5 m | 20 °C | PVC | 2×90°, 1 gate, 1 check, 1 foot | 1.0 m/s | Recommended ID ~ 32–38 mm |
Suction piping strongly influences pump stability because any restriction reduces inlet pressure. In garden pumping, common symptoms of undersized suction lines include noisy operation, vibration, fluctuating flow, and frequent loss of prime. A conservative suction diameter helps keep friction losses low, protects seals and impellers, and improves startup reliability when the source level varies during watering.
As a rule of thumb, suction velocity is typically kept around 0.6–1.2 m/s for small centrifugal and jet pumps. Lower velocity reduces turbulence and air release, especially when drawing from a tank, sump, pond, or shallow well. If the suction line includes a strainer, check valve, or multiple elbows, target the lower end of the range to maintain steady inlet conditions.
Total suction loss equals straight-pipe friction plus minor losses from fittings. This calculator uses Darcy–Weisbach with a friction factor based on Reynolds number and pipe roughness. Minor losses are expressed as K·(v²/2g). Typical K values often used for planning include about 0.9 for a 90° elbow, 2.0 for a check valve, and 3.0 for a foot valve, though products vary.
Cavitation risk increases when NPSH available (NPSHa) approaches the pump’s NPSH required (NPSHr). NPSHa is reduced by suction lift, warm water (higher vapor pressure), and suction losses. For practical field work, maintaining at least 1 m margin over NPSHr is a common conservative target. If NPSHa is low, reduce lift, shorten suction length, or upsize the suction line.
Keep suction piping short and straight, minimize high points that trap air, and seal threaded joints carefully. Use a full-bore valve on suction and avoid unnecessary reducers. Ensure strainers are sized for the flow and kept clean. Confirm the pump curve point (flow and head) and then verify NPSHr at that flow, especially for higher lifts or warmer climates.
For many garden pumps, 0.6–1.2 m/s is a practical range. Use lower values when the lift is high, the suction line is long, or you have multiple fittings, strainers, or valves.
Water temperature affects density, viscosity, and vapor pressure. Warmer water lowers NPSH available, increasing cavitation risk. It can also change friction slightly by changing viscosity.
It’s optional, but recommended. If you enter NPSHr from the pump curve at the same flow, the calculator can show a margin. A larger margin generally means quieter, safer operation.
Strainers add minor loss and can clog over time. Include it in the fitting count, keep suction velocity conservative, and inspect regularly. A clogged strainer can cause sudden flow drop and noise.
Foot valves can introduce significant resistance on the suction side. If you must use one for priming, consider upsizing the suction line and minimizing other fittings to preserve inlet pressure.
This tool is tuned for clean water. Other fluids may have different density, viscosity, and vapor pressure, which can change friction and NPSH significantly. For chemicals or slurry, use fluid-specific data.
Yes. Suction lines are often larger than discharge lines to reduce losses and avoid cavitation. A larger suction pipe can improve priming and reduce noise, especially with higher lifts or warm water.
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.