Dilutions for the GEL EC CFU Kit

Add 10 mL sample and 90 mL
E. coli free water to Thio-Bag

Pour GEL EC growth medium into Thio-Bag

Pour GEL powder into GEL bag

Complete remaining testing procedures

The Aquagenx GEL EC CFU Kit was originally designed to test drinking water sources. However, the GEL Kit is easily adapted for surface waters higher concentrations of bacteria or higher allowable limits of bacteria.

This is accomplished by diluting GEL samples. The sections below provide 1:10 dilution guidance. The GEL EC CFU Kit can be used to analyze 100 mL water samples but it may be difficult to count E. coli colonies if colonies are over 500 CFU/100 mL.


​Dilution water needs to be free of E. coli, preferably sterile water, such as:


  • Standard Methods phosphate buffer
  • Autoclaved or boiled reagent water
  • Autoclaved or boiled tap water
  • High quality, certified bottled water. Some bottled waters are produced locally and are microbiologically unsafe.
  • Distilled water from a commercial source and sold in properly sealed bottles. While not necessarily sterile, it should be free of E. coli.

Surface Waters

The Aquagenx GEL EC CFU Kit can be used to test rivers, streams, creeks, marine waters and fresh recreational waters for E. coli using a 1:10 dilution.

1:10 Dilution

Steps for 1:10 dilution:

  • Collect 10 mL sample with a pipette
  • Add 10 mL sample to Thio-Bag
  • Add 90 mL diluent to Thio-Bag (fill Thio-Bag to 100 mL fill line)
  • Add our E. coli (EC) growth medium to Thio-Bag and dissolve the medium
  • Pour contents of Thio-Bag into GEL bag
  • Proceed with remainder of testing procedures

→ 1:10 Dilution instructions for surface waters are found in Product Documents