TANDEM FILTER CAPACITY (0.5m2 TO 7.0m2)
This table assumes that you have determined the plant flow required for a specific application. It also assumes that you have decided to use a tandem backwash system, with two filters arranged in parallel to “filter” at a flow rate of 21m3/hr/m2. In this case, the filters are individually backwashed with the full duty of the pump to achieve the required backwash rate of 42m3/hr/m2.
- The nominated backwash flow (in l/sec) is based on a backwash rate of 42m3/hr/m2. Subject to the type of filter media being used, this rate may vary.
- Pumping equipment should be selected to provide the required “backwash flow”.
- Filters with up to 3.5m2 of filter area may use single lever multiport valves; larger systems use commercially available valves arranged as either, a four or five valve matrix
- Larger plant capacities can be satisfied by using a number of tandem systems. Alternatively, a multiple tank system using a shunt backwash method may be considered