Turbidity
A measure of water clarity — how much suspended particles scatter light passing through water.
ADWG Guideline
5 NTU
Turbidity measures how cloudy or hazy water appears. It is caused by tiny suspended particles — sediment, organic matter, algae, or clay — that scatter light.
Why it matters
The ADWG sets a guideline of 5 NTU for aesthetic quality. High turbidity can:
- Indicate the presence of pathogens that attach to particles
- Reduce the effectiveness of chlorine disinfection
- Cause an unpleasant appearance, though not necessarily a health risk at moderate levels
Water treatment plants target turbidity well below 1 NTU in filtered water.
How it’s measured
Turbidity is measured in Nephelometric Turbidity Units (NTU) using a nephelometer, which shines a light beam through the water and measures scattered light at a 90-degree angle.
Check Your Water
See how turbidity levels compare in your suburb with real water quality data.
Disclaimer: Glossary definitions are provided for general educational purposes only and do not constitute medical advice or professional guidance. For specific health concerns about your drinking water, consult a qualified health professional. See our Terms of Use.