Chemical Monitoring Directions
Turbidity Instructions

Prepared by Deana Crumbling

Turbidity is the measure of the cloudiness of water. It is important because…

Remember: It is more accurate to perform the test immediately at stream-side. To do so, you must take along a small bottle of tap water.

  1. Fill one of the cylinders to the 50 mL mark with stream water and the other with tap water. If the water appears very turbid/cloudy, fill the cylinders only to the 25 mL mark.
  2. SHAKE the bottle of Standard Turbidity Reagent vigorously to resuspend the latex particles in the reagent.
  3. To the cylinder containing TAP WATER, use the dropper to add Standard Turbidity Reagent in 0.5 mL increments-(NOT drop-by-drop). Add 1 squirt of 0.5 mL Reagent, then use the plastic stirring rod to mix.
  4. Compare the fuzzy appearance of the black dot at the bottom of the tap water cylinder with the dot in the stream water cylinder (DO NOT try to match the color-the latex particles are white and will never match the brownish or greenish tint of most stream water). The goal is to add enough of the Standard to the tap water so that the cloudiness (as judged by the appearance of the black dots) of the tap water is made to match that of the stream water.
  5. Count the number of "squirts" required to get a match. Read the turbidity (in units called JTU) off the chart on the kit's package insert/directions. Make sure you read off the correct column-one column is for use with a 50-mL volume, the other column is for a 25-mL volume.
  6. On the reporting sheet, fill in the result and the number of squirts and test volume used. Examples: 15 JTU (3 squirts/50 mL) or 30 JTU (3 squirts/25 mL)
  7. If the stream water looks just as clear as the tap water, report the result as "less than 2.5 JTU" by circling that option on the SOS Report Sheet.
  8. If the stream water looks a little more cloudy than the tap water at the start, but when you add 1 squirt of turbidity reagent it looks like the tap water column becomes much cloudier than the stream water, report the result as "about 2.5 JTU" by circling that option on the Sheet.

Tip: If you are not sure if you have a match, add another squirt of turbidity reagent. If you can see that you've "gone ever," you can feel sure that the previous number of squirts was indeed the correct number.

Note: You may interpolate your result, if you wish. For example, if the match seems like it was between squirts 2 and 3 for a 50 mL volume, you could report the result as " ~12.5 JTU" (which means "about half-way between 10 and 15 JTU"). Or you could use the higher number (15 JTU) or the lower number (10 JTU), whichever one you feel is closest to the match. Any of these choices is acceptable, since the turbidity measurement is only an estimate.

Turbidity Test Results
Number of Measured Additions Amount in mL 50 mL Graduation 25 mL Graduation
1 0.5 5 JTU 10 JTU
2 1.0 10 JTU 20 JTU
3 1.5 15 JTU 30 JTU
4 2.0 20 JTU 40 JTU
5 2.5 25 JTU 50 JTU
6 3.0 30 JTU 60 JTU
7 3.5 35 JTU 70 JTU
8 4.0 40 JTU 80 JTU
9 4.5 45 JTU 90 JTU
10 5.0 50 JTU 100 JTU
15 7.5 75 JTU 150 JTU
20 10.0 100 JTU 200 JTU