Testing Services

Bacteriological Water and Wastewater Testing

The Environmental Services Laboratory offers Bacteriological Water Testing to water utilities, construction and other private businesses, laboratories and private well and home owners.

Bacteriological water testing is used for the detection and identification of

  • Total Coliform in Water
  • E.coli in Water and Wastewater

What is Total Coliform and E.coli?

Coliform organisms are bacteria commonly found in humans, animals and the environment.  Their presence in water indicates that conditions in the water supply may also support the existence of other microbes, including pathogens.  Pathogens are microbes (germs or “bugs”) that cause illness.  Coliform bacteria may not cause illness but they indicate that conditions are suitable for the existence of other microbes that can cause illness.  The presence of E.coli bacteria is evidence of recent contamination of the water by animal or human feces.

Sample Containers

Samples must be submitted using laboratory-issued, sterile collection bottles.  Bottles are available at the Environmental Services Laboratory Monday through Thursday from 8 a.m. to 4 p.m.

Sample Collection

Proper sample collection is the responsibility of the submitter.  The Environmental Services Laboratory has developed Standard Operating Procedure #01-28-09, Bac-T Sample Collection, Transportation, and Storage for External Customers.  You are encouraged to review this document in its entirety:

The basic steps are outlined below:

Sample Site Preparation for Drinking Water Samples

  1. Select a faucet that will be a representative sample of the main water source.
  2. Remove any aerator, strainer or any other device that would restrict the free flow of water from the tap selected.
  3. Allow water to run 2 to 3 minutes.
  4. Turn water off, if possible, and disinfect the tap with bleach or alcohol.
  5. Turn on and adjust the water flow to a slow and steady stream to permit filling the container without splashing.

Sample Collection

  1. Unscrew the bottle cap carefully and hold it in one hand while filling the bottle.  Do not touch the inside of the cap with your hand.
  2. Fill the bottle slightly above the 100 ml line etched on the container.  Samples that do not contain the minimum 100-ml volume cannot be accepted.
  3. Replace cap carefully and close tightly to avoid leakage.
  4. Turn off tap.
Correct Sample Volume

Correct Sample Volume

Some DON’Ts to ensure proper collection

  • Don’t rinse out the container
  • Don’t touch the inside of the container or cap
  • Don’t allow the container to touch the water tap
  • Don’t fill the container to overflowing

Sample Storage

It is recommended to refrigerate the sample if it is not immediately submitted to the Environmental Services Laboratory.  Do not freeze the water sample.

Sample Hold Times

  • Drinking water samples must be received within thirty (30) hours of collection.
  • Wastewater, pool/spa, and river/lake and rainwater samples must be received within six (6) hours of collection.

Sample Transport

It is recommended to place the sample in a cooler or Ziploc bag with loose ice or an ice pack to keep it cool during transport.

Chain-of-Custody Forms

Chain-of-custody forms are available at the Environmental Services Laboratory.


Test Results

Test results are available on the day following sample submission.  A preliminary report by facsimile or e-mail will be provided upon request.

What do the results mean?

  • If neither Total Coliform nor E.coli bacteria are detected in the water sample, the water is deemed potable.
  • If the sample tested positive for Total Coliform bacteria, conditions are suitable for the existence of other microbes that may cause illness.  The water should not be consumed without proper treatment.
  • A positive test result for E.coli bacteria indicates that the water supply has a connection with some unsanitary source.  The water should not be consumed without proper treatment.

Reporting Responsibilities

  • Drinking Water from Public Water System
    • Laboratory will report positive Distribution, Repeat and Raw results to TCEQ within 24 hours.
    • Laboratory will report all results to TCEQ by the tenth (10th) day of the following month.
  • Private Well Water
    • Submitter is responsible for reporting results.
  • Wastewater
    • Submitter is responsible for reporting results.
  • Ambient Water (pool/spa/lake/river, rain)
    • Submitter is responsible for reporting results.
  • Ice Machines, Bottled Water Vendors
    • Submitter is responsible for reporting results.

Calibration Verification of Field Chlorine Instruments

The calibration verification test is designed to fulfill the requirement of Texas Administrative Code (TAC) 290.46(s)(2)(c)(i), whereas the accuracy of manual disinfection residual analyzers shall be verified at least once every thirty (30) days using a chlorine solution of known concentration.

Please contact the laboratory for testing times.  The lab can be reached via phone at (512) 218-5561 or via e-mail at Laboratory Questions.