Fact Sheet 2.33
• cross or other murk on the bottom of the tube.
• Slowly pour the water sample into the tube, waiting for air bubbles to rise if
necessary, until the mark on the bottom of the tube just disappears.
• Stop pouring the water sample into the tube and look at the level of water in the
tube. For turbidity tubes which have a turbidity scale marked on the side, read the number on the nearest line to the water level. This is the turbidity o f the water. I f the tube does not have a scale marked, measure the distance from the bottonz o f the tube to the water level with a tape measure and look up or calculate the turbidity o f the water sample using the instructions provided with the tube.
• After use, wash the tube in clean water and store the two parts of the tube where they cannot be damaged.
Turbidity guidelines for drinking water
For drinking water supplies, the following guidelines should be taken into consideration :
• Drinking water should have a turbidity of 5 NTU/JTU or less. Turbidity of more than 5 NTU/JTU would be noticed by users and may cause rejection of the supply.
• Where water is chlorinated, turbidity should be less than 5 NTU/JTU and preferably less than 1 NTU/JTU for chlorination to be effective.