Turbidity Tube Conversion Chart

    Turbidity Tube Conversion Chart

    The Turbidity Conversion Chart converts the measured value in cm to Nephelometric Turbidity Units (NTUs).  This is the official unit of measurement to quantify how much light is scattered due to the suspended sediments.  You can convert your turbidity tube reading from a height to NTUs using the chart below.

     

    Distance from bottom of tube (cm)

    NTU's

    < 6.25 > 240
    6.25 to 7 240
    7 to 8 185
    8 to 9.5 150
    9.5 to 10.5 120
    10.5 to 12 100
    12 to 13.75 90
    13.75 to 16.25 65
    16.25 to 18.75 50
    18.75 to 21.25 40
    21.25 to 23.75 35
    23.75 to 26.25 30
    26.25 to 28.75 27
    28.75 to 31.25 24
    31.25 to 33.75 21
    33.75 to 36.25 19
    36.25 to 38.75 17
    38.75 to 41.25 15
    41.25 to 43.75 14
    43.75 to 46.25 13
    46.25 to 48.75 12
    48.75 to 51.25 11
    51.25 to 53.75 10
    53.75 to 57.5 9
    57.5 to 60 8
    Over the top
    6

     

    In addition, the water quality standards for NTUs in Utah is:

      • An increase of more than 10 NTUs over natural levels is considered unacceptable for:

    - Recreation and Aesthetics (2)

    - Warm-water fisheries (3B)

    - Cold-water fisheries (3A)

     

      • An increase of more than 15 NTUs over natural levels is considered unacceptable for:
        - Non-game fish and other aquatic wildlife (3C)

    - Waterfowl, shore birds, and water oriented wildlife (3D)