Which Hach benchtop turbidity meter should I choose? What’s the difference between TU5 and TL23 Turbidity meters?

Q: I am looking for a new benchtop turbidity meter, but Hach offer two versions – the TL23 series and the TU5 series.

Which turbidity meter should I choose?

What is the difference between the TU5 and TL23 models?

TL23 TU5

A: There are many differences between the two ranges, as explored below;


TL23 Series – for a wider range of applications, a lower cost option using traditional tried and tested technology.

TU5 Series – primarily for clean water applications (some stages of drinking water analysis, power plant and food and beverage manufacturing sites). These higher specification units offer additional features like RFID sample recognition, 360°x90° detection technology, and seamless comparison between lab and online results when using a TU5 online system in plant.



Looking at the differences in further detail, by application;

TU5 Series Benchtop Turbidity Meter
TU5 Series Benchtop Turbidity Meter

The TU5 series is recommended for;

  • Drinking water
    • Clarifier effluent
    • Filter effluent
    • Distribution system
    • Elevated tank
  • Power
    • In plant water testing
  • Food and beverage
    • Discharge to environment


The TL23 series are recommended for;

TL23 series benchtop turbidity meter
TL23 series benchtop turbidity meter
  • Drinking water
    • Raw water
    • Clarifier effluent
    • Filter backwash
  • Wastewater / Food and beverage
    • Raw sewage
    • Aeration basin
    • Reverse activated sludge
    • Thickening / digestion
    • Secondary clarification
    • Discharge to environments
  • Power
    • Raw water when using river water source
  • High salinity applications
    • Desalination plants
    • Seawater testing


Technology / Specifications

The two ranges vary in their specifications also, so this may be considered when choosing the right model for your needs;

Specification TL23 Series TU5 Series
Light source Tungsten filament lamp (for EPA versions)

LED at 860nm ± 30nm (for ISO versions)

Class II Laser light source
Accuracy ±2% of reading plus 0.01 NTU from 0 to 1000 NTU

Can be ±5% or more from 1000 NTU upwards

(varies slightly with exact model, see datasheet for full details)

±2% of reading plus 0.01 NTU from 0 to 40 NTU

±10% of reading from 40 to 1000 NTU

Silicone oil required? Yes No
RFID sample recognition? No Yes
Touch screen control Yes Yes
USB ports for results saving to USB stick Yes Yes

NB many of the specifications cannot be directly compared or require more in depth consideration – please see the full datasheets for each version by following the links above



Overall the TU5 series present an excellent option if you need to compare results to an online monitor of the same family, or if you are working with very clean and low turbidity samples.

For general use or for samples with higher turbidities, the TL23 series offer a great testing option with all of the features and compliance you would expect of a modern turbidity meter.


For more information on either range just follow the links above or contact us if you have any questions;