Measuring pool water turbidity or cloudiness - why is my pool water cloudy?

Swimming pool water can sometimes appear cloudy. This is known as turbidity, and can be monitored and measured with a turbidity meter (aka turbidimeter). We've taken a look at what causes cloudy pool water, how to monitor and measure it and how to correct and control it.

What causes cloudy pool water?

The Pool Water Treatment Advisory Group (PWTAG) is the independent UK authority on pool water standards and quality. They report several factors that can cause cloudy looking pool water in their technical note on the subject;

• Bacterial growth
  • Potentially caused by;
    • low free chlorine levels - so bacteria are not being sanitised
    • a failed circulation pump - so water is not being filtered and disinfected
    • a high pH - so disinfection methods are not adequate (the optimum pH is 7.2 to 7.4)
• Excessive air in the water - possibly due to a failed pump seal
• Localised areas of high pH - by dosing an alkaline chemical at one point, water hardness (limescale) can precipitate out
• Powdered chemicals not dissolved properly before addition to the pool
• Incompatible cleaning materials
• Excessive water hardness
• Inadequate filtration

 

What level of cloudy water is acceptable in a swimming pool?

PWTAG recommends that pool water should be no more than 0.5 NTU. This gives a good overall indicator of clarity and cleanliness. This equates to a very low level - just see the scale below which only starts at 10 NTU [caption id="attachment_3970" align="aligncenter" width="528"] The turbidity scale is measured in NTU, as shown above[/caption]  

How can I measure and monitor cloudy pool water?

Use a turbidity meter to quickly and accurately measure the cloudiness of pool water. These electronic devices work by passing light through a sample of the water and measuring how much is scattered or reflected. Simply fill the sample cell, place it in the unit and press read. Results appear on the screen in around 30 seconds. [caption id="attachment_3977" align="aligncenter" width="391"] TurbiCheck Turbidity Meter[/caption] The Lovibond Turbicheck unit or the Palintest Turbidity meter are both suitable for accurate testing at the levels required for pool water, and come with everything required to start testing included. The units are both simple to use, and come with an instruction manual for reference. For more information about turbidity and other pool water tests, follow the links above or contact us with any questions;