Back wash rasin in planning each season because of water quality will vary according to each season (the conductivity of water is different, which will result in the need to increase ion trap rasin)
Plan a back wash rasin each season. The water quality will vary according to the seasons (the conductivity of the water is different, which will result in the ion trap rasin be increased).
Planning back wash rasin in each season, the water quality will vary according to each season (the conductivity of different น้ำจะ which will result. Rasin to trap ion increase).