Modified Colitag™ 16-Hour Presence-Absence Test

Modified Colitag

Hach Modified Colitag™ is the fastest coliform presence-absence test in the market. Test your water at 5:00 pm and have your results by 9:00 am the next day!  The product also provides unparalleled flexibility by offering two testing parameters (16 or 22 hour test) in one product.

The fastest on the market at 16 hours

  • Fastest EPA-approved test for coliforms and E. coli
  • Test as late as 5:00 PM and still have results by 9:00 AM the next day

One product that supports 16- or 22-hour test methods

  • Allows for a "standard" test that requires less setup, or a "rapid" test when necessary
  • One media for both tests reduces complexity in certification and inventory

Results are valid for up to 32 hours

  • Saturday’s tests can be read on Monday – no need to work all weekend
  • Results stay valid for 8 times longer than the competition

Learn More or call 800-227-4224

Hach Modified Colitag Procedure

Snap to Open Hach Modified Colitag

Step 1: Snap to open Hach Modified Colitag Pack

Shake to dissolve media

Step 3: Shake sample, media will not dissolve immediately

Check for yellow color

Step 5: Check for yellow color, indicating coliforms

Add Hach Modified Colitag to water

Step 2: Add Hach Modified Colitag to 100 mL water sample


Step 4: Incubate for 16-22 Hours at 35°C ±0.5°C

Check for e coli

Step 6: Check for fluorescence with UV light, indicating E. Coli

Regulatory Information

US Map

To get started using Modified Colitag in your state, and to access contact information for your state regulator, please visit our interactive map.

Additional Regulatory Approval Information

What is a Coliform?

A coliform is any of a number of organisms whose presence in wastewater is an indicator of pollution and of potentially dangerous bacterial contamination.

E. Coli is a coliform species found in the intestinal tract of warm-blooded animals. - its presence can be indicative of fresh pollution from human or animal waste.