The PLC progress preset filtering period
and multiway valve control preset backwash time before the equipment leave factory.
Until filtering period is over, the backwashing period is starting, open backwash
electrical valve, start inlet water pump, open electrical valve of each filter, stop
chemical metering pump, and then square impact washing and backwashing is
starting, the time of square impact washing and backwashing can set on the control
panel of multiway valve, when the backwashing period is over, the filter will wait for.