Water treatment/ CALCULATOR
Check the backwash flow required by a cylindrical media vessel against the water supply available at the filter.
FROM ESTIMATE TO ACTION
Use the vessel’s internal diameter in mm, not the pipe diameter, and the media manufacturer’s backwash loading in m/h at the relevant water temperature. Loading is flow per bed area, not L/min or a duration. The illustrative 250 mm vessel at 30 m/h requires about 24.5 L/min; neither number is a universal setting.
Use sustainable flow available at the filter at the required backwash pressure, not a pump’s maximum free-flow rating. With 35 L/min available the example margin is about +10.5 L/min; with 20 L/min it is about −4.5 L/min. A negative margin indicates a modeled shortfall; longer duration does not supply the missing flow. A positive margin alone does not verify pressure, valve losses, bed expansion or drain capacity.
At the required flow, the 10-minute example step uses about 245 L. This is calculated demand, not measured consumption when the supply falls short. The calculator covers one constant-flow backwash step, not the entire regeneration sequence. Calculate other water-using stages separately with their own flows and durations, then sum them without counting the same step twice. Check refill/recovery and drainage separately; the result is not an automatic tank or drain size.