For a single flush WC, enter the flushing volume (litres) into column (a) and the quantity (no.) into column (b). Where there are multiple single flush fittings with the same flushing volume, follow the same procedure.

  1. For dual flush WCs, tick the ‘Dual Flush’ box in column (a). There will now be 2 values to input into column (a): the full flushing volume and the part flushing volume.
  2. Where multiple WCs are specified with various flushing capacities, tick ‘Multiple Fittings’ in column (a). For each flushing capacity, enter the flushing volume (into column (a)) and the quantity (into column (b))
  3. Click ‘Calculate’ to calculate the average effective flushing volume.



*The effective flushing volume for dual flush WCs is calculated as follows:

= (Full flushing volume (litres) x 0.33) + (part flushing volume (litres) x 0.67)