RO 90 - Waste Water Ratio Test

Purpose: The RO takes 4-5 gallons of waste water to make 1 gallon pure water. So the "Waste Ratio" should be 4:1 to 5:1.

If waste water is less than this ratio, the TDS will be high. See Figure 1 for reference point.

Test waste ratio as follows:

  • Close the tank valve.
  • Remove the BLACK drain line from the drain saddle. Put line in a bucket to catch the waste water.
  • Remove the clear line from Point C3 on the ASO. Pure water will flow out of the line in a small stream.
  • Fill up an 8oz cup from this line ---> this is the PURE water from the membrane.
  • Measure the amount of WASTE water in the bucket ---> Are you getting about 4 - 5 cups?
  • Record the amount of waste water in bucket. Let us know the "Waste Ratio".
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