Plan your filter in minutes with clear inputs. Compare existing tanks or auto-size new ones. Download reports, validate flow splits, and reduce clogging risk.
| Scenario | Total Flow (m³/h) | Filters | Target HRT (min) | Depth (m) | Suggested Diameter (m) | Upflow (mm/s) |
|---|---|---|---|---|---|---|
| Backyard pond | 1.20 | 1 | 6 | 0.80 | 0.46 | 2.02 |
| Small grow beds | 2.50 | 2 | 5 | 0.90 | 0.40 | 2.73 |
| Heavy solids load | 4.00 | 3 | 8 | 1.00 | 0.50 | 1.89 |
A radial flow filter slows incoming water and spreads it outward, allowing heavier solids to drop before clarified water exits near the surface. The inlet energy, baffle geometry, and outlet height influence separation. The calculator focuses on hydraulics: it splits total flow across parallel filters, converts units, and estimates tank volume and velocities so designs can be compared consistently.
Retention time is the average time water stays inside the vessel. The calculator uses V = Q × t and applies a safety factor to cover turbulence, short-circuiting, and future loading. For many pond and bed systems, designers often explore 3–10 minutes, then confirm with observation: clarity, settled sludge depth, and how often purging is required. Higher loads typically need more time or more parallel units.
Upflow velocity is computed from flow per filter divided by plan area. Lower values generally support settling because particles have more opportunity to sink against the upward motion. A common starting target is keeping upflow in the low millimetres per second range, then tuning with real results. The report also shows inlet pipe velocity, which helps confirm the feed line is not creating excessive jetting into the tank.
Adding vessels in parallel reduces Q per filter, lowering upflow velocity and often improving separation without increasing depth. It can also shorten cleaning time because each unit holds less sludge before performance drops. The safety factor increases required volume, giving a buffer for seasonal biofouling, pump upgrades, and imperfect flow balancing between outlets, valves, or manifolds.
Use the “check existing tank” mode to confirm that current diameter and depth still meet your target retention. If the calculator flags high velocities or low time, consider throttling flow, increasing diameter, adding a second unit, or improving inlet diffusion. Routine purging of settled solids preserves effective volume and keeps downstream bio-media cleaner, which stabilizes flow and reduces clogging in grow beds.
It increases required tank volume by a chosen percentage. This cushions real-world effects like turbulence, uneven splitting, and gradual fouling, so retention time stays closer to your target.
Use auto-size when planning a new vessel and you know your intended depth. Use check mode when you already have a tank and want to see if it meets retention and velocity goals.
Parallel units divide total flow, lowering flow per filter. That reduces upflow velocity and can improve settling performance while keeping each vessel easier to service.
Many systems start exploring 3–10 minutes, then adjust based on solids load and clarity targets. Higher loads often benefit from more time or additional parallel units.
The score is a transparent heuristic based on retention time and upflow velocity only. Use it to compare design options, not as a guarantee of filtration performance.
High pipe velocity can cause jetting and re-suspension. Consider increasing pipe diameter, adding diffusers, or smoothing the inlet path so water enters calmly and spreads evenly.
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.