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The Natural Balance Type Rapid Sand Filter is an economical filtration device with a streamlined structure.
Neither backwash pumps nor elevated tanks are necessary since backwash is performed using the difference in level between the treated water channel and the sand layer.
By means of this feature, reduction of operation and maintenance costs can be achieved.


Two filtration tanks are integrated as one unit which shares a treated water channel.
While one filtration tank performs the backwashing process, the treated water from the other filtration tank is used as backwash water.
The water level drops to the drainage trough during the backwashing process, and the treated water washes the sand layer due to the difference in level with the treated water channel.


During backwash


  1. Even distribution of incoming raw water
    The incoming raw water is distributed evenly for each tank in a unit even when the flow rate is variable.
  2. Low operating cost and less maintenance management
    The drive area has only a compressor for an air valve, so the operating cost is low and there is less maintenance management.
    Also, the number of valves is small, making operation easier.
  3. Noise reduction
    No siphon valve is used, so there is no noise caused by shutting off the siphon.
  4. Low construction cost and small footprint
    There is no need for a backwash pump or elevated water tank, so the construction cost is low and less space is needed for installation.

(In-house comparison)


  • Water purification plant

Standard Dimensions

Standard Dimensions
Treatment water quantity Width
Number of tanks
10,000m3/d 13 15 5.5 8
25,000m3/d 15 29 5.5 8
50,000m3/d 19 45 5.5 12
100,000m3/d 22 77 5.5 14