Riser Tube/ Abs Pipe
Cheap and easily available PVC pipe are made for water to flow through the internal wall. However, when installed in the filter tank, water also comes in contact with the external wall and allows the sand media to rub against the external wall of PVC pipe during backwash.
Cleaning off the printed data with solvent and filling the sharp edge of thepipe are simple alterations we make to perfect the tubes.
Discard Top Strainer
No large-scale professional sand filter would install a top strainer in their system because it restricts the trapped sediment from draining out efficiently during backwashing.
We can afford to discard it because we only load the entire media into the tank on-site, during installation. Contrary to the pre-filled media tanks in the market, we do not have to worry that the already filled-in sand would run into the multi-port valve during transportation.
Sizing of Sand Media and Tank with Well-Known Engineering Factors
The following engineering factors are widely recognised by water treatment professional worldwide, in sizing the tank coupled with specific sand media:-
Service flow (gpm/sq ft) : 3-5
Backwash flow (gpm/sq ft) : 15-20
From the above figures, the required flow for backwashing is obviously much higher (around 4 times) than that of the service flow. The reason behind such strong flow during backwashing is to ensure sufficient lifting force to efficiently dislodge the trapped sediments against gravity. However, during service run, slower flow ensures better filtered water quality.