21st May 2013 at 4:00 pm #849
Flow rate for any kind of slow sand filter should be in the range of 0.1 to 0.4 m3/m2/hour. The larger the area, the more flow, so it seems your calcs are more or less correct. Below my calcs:
Round concrete filter:
Diameter: 0.26 m
Area: 0.0531 m2
If 1m2 can have a maximum of 400 litres/hour flow rate, then 0.0531m2 can have maximum 21.23 litres/hour
Metal drum filter:
Diameter: 0.584 m
Area: 0.2677 m2
If 1m2 can have a maximum of 400 litres/hour flow rate, then 0.2677m2 can have maximum 107.09 litres/hour