The polishing step. Sedimentation takes the bulk; the filter takes what is left. Coarse anthracite on top does the depth filtration, fine sand below acts as the final barrier — and the whole thing runs until headloss or breakthrough says stop.
The panel opposite runs the same correlations as the F-400 design sheet, so the animation and the calculator cannot disagree. Every parameter below is live — drag one and the picture responds.
| Parameter | Unit | Default | Range |
|---|---|---|---|
| Configuration | |||
| Filter type | Gravity rapid sand | 3 options | |
| A pressure filter has head to spare, so it runs faster. A continuous filter never stops to backwash, so its run length stops being a design variable at all. | |||
| Duty | |||
| Feed flow | m³/h | 200 | 20 – 1,200 |
| Influent SS | mg/L | 12 | 1 – 60 |
| Filter area (each) | m² | 12 | 2 – 60 |
| Filters in service | off | 3 | 1 – 10 |
| Anthracite depth | mm | 600 | 200 – 1,200 |
| Sand depth | mm | 300 | 150 – 800 |
Open the full F-400 design sheet for the other five inputs, all twenty-five results with their envelopes, the five equations printed beside the numbers they produce, and a calculation record you can export and put in a design file.
Six of the eleven inputs the F-400 design sheet takes.
A pressure filter has head to spare, so it runs faster. A continuous filter never stops to backwash, so its run length stops being a design variable at all.
This page sizes the unit on six variables and tells you whether the headline numbers land in range. That is enough to sketch with, and it stays free. What it will not do is survive a design review: it does not show you the equation behind any number, it checks the obvious limits rather than all of them, and there is nothing to file.
The F-400 design sheet runs the same physics on eleven inputs, reports twenty-five results against their envelopes, prints the five governing equations beside the numbers they produce, and exports the lot as a calculation record for the design file.