Plan siphons for ponds, barrels, and irrigation tasks. Compare pipe materials and fittings in minutes. Get a recommended diameter and printable results instantly here.
Use these values to test the calculator quickly.
| Use case | Flow | Length | Static head | Crest rise | Bends | Material | Typical output |
|---|---|---|---|---|---|---|---|
| Rain barrel to bed | 15 L/min | 6 m | 0.8 m | 0.3 m | 2 | Smooth plastic | ~19–25 mm inner diameter |
| Pond water change | 40 L/min | 12 m | 1.5 m | 0.7 m | 4 | Rubber hose | ~32–38 mm inner diameter |
| Tank to drip header | 25 L/min | 8 m | 1.2 m | 0.6 m | 3 | Smooth plastic | ~25–32 mm inner diameter |
The calculator sizes the pipe so total head losses fit within usable head.
A lift check estimates safe crest rise using atmospheric head and water vapor pressure at your temperature and altitude.
A garden siphon works because elevation difference converts to flow energy. This calculator links your target flow to pipe diameter, so the available head is not wasted by friction. When you size correctly, transfer stays steady, starts faster, and avoids noisy surging that can stress plants and fittings. It also helps match flow to gentle watering, not soil erosion.
Total length, bends, valves, and strainers all add resistance. Minor losses are grouped with a K value, while straight runs use Darcy–Weisbach friction. Enter realistic fittings counts, and add extra K for quick couplers, tees, reducers, or kink-prone hose sections commonly used in beds and barrels. If you use long corrugated hose, expect higher losses than smooth tubing.
Diameter drives velocity, and velocity drives losses by v². Doubling diameter increases area four times, lowering velocity sharply for the same flow. Lower velocity reduces friction, reduces entrance and exit losses, and gives more margin when the outlet level changes. The standard-size suggestion helps you buy practical tubing. For clean starts, keep diameter consistent instead of using step-down adapters.
Siphons also have a height limit at the crest. As the high point rises, pressure drops and bubbles can form. Temperature and altitude reduce safe lift by raising vapor pressure and lowering atmospheric pressure. Use the lift check to keep the crest below the recommended limit and prevent breaking prime. A screened inlet prevents debris, but it should not be undersized. Check connections for leaks; even small air ingress stops flow.
After you submit, compare total loss to usable head. If losses are close to the limit, choose the next larger size or shorten the run. If velocity is very high, expect vibration and more air entrainment. If drain time matters, enter volume to estimate how long a water change or barrel emptying will take. Document your settings to repeat the same setup each season.
Static head is the vertical difference between the source water surface and the outlet level. More head generally increases flow, unless friction and fittings consume it.
Real siphons face air pockets, small leaks, and changing levels. A safety margin keeps the design conservative so the target flow is still achievable during typical garden use.
Count any turn that behaves like an elbow, including tight curves, kinks, and sharp loops over a rim. For gentle sweeping bends, you can count two bends as one.
About 0.5 to 2.0 m/s is usually comfortable. Lower speeds may prime slowly, while higher speeds raise losses, noise, and the chance of pulling air at the inlet.
As water rises to the crest, pressure drops. If it approaches vapor pressure, bubbles form and the siphon loses prime. Warm water and high altitude reduce the safe lift.
If your run is long, fittings are many, or losses are close to usable head, choose the next larger size. It lowers velocity, improves reliability, and reduces priming effort.
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.