Bacteriological Sampling - PUB3091

Individual water systems are required to submit samples of their water for laboratory testing to verify the water they are serving to the public meets all federal and state standards. Please contact the department's Regional Office that assists your county, to discuss the sampling procedures, sample siting plan (routine and repeat sites) and sample collection schedule (planned rotation of sample sites throughout the year or season of operation) revisions, and assessments.

Sampling Schedule

How often and where samples are taken varies by system and contaminant and is detailed in the department's Bacteriological Sampling Calendars. Systems using independent laboratories are responsible for ensuring the sample results are submitted to the department by the 10th of the following month.

Sampling Procedures

The following instructions are specifically for systems using sample bottles provided by the Missouri Department of Health and Senior Services' State Public Health Laboratory.

Sample Containers

Bacteriological water analysis sampling bottles can be requested two ways:

1. Enclosed postcard that comes with the sample bottles
2. Online Sampling Bottles Request Form

These sample bottles contain a chlorine neutralizer, either in liquid or crystalline form. Do not rinse the contents from the container. The bottles are sterile and ready for use when shipped. 

Sample Collection

1. Gather all of the sampling supplies before you begin. Be sure to wash your hands thoroughly before handling the supplies.
2. Go to the sampling location(s) specified in the system’s written bacteriological sample siting plan and sample collection schedule. You will want to take the sample from a clean, smooth-nosed, cold-water tap if possible. Avoid drinking fountains, leaky faucets and frost-proof yard hydrants, since it is not practical to sterilize these fixtures.
3. Remove any aerators, strainers, gaskets or hoses that may contain bacteria.
4. Open the cold-water tap (or hot water if a mixing faucet is used), and let the water run for approximately three minutes. This should adequately clear the water line.
5. Flame-sterilize or chemically disinfect the tap. 
   • Do not flame-sterilize if the tap is plastic or has aerators attached. 
   • Chemically disinfect the tap by thoroughly rinsing both the inside and outside of the tap with a mixture of 50% department-approved sodium hypochlorite (bleach) and 50% tap water. Chemical disinfection alternatives include using ethyl alcohol greater than 60% or Isopropyl alcohol (rubbing alcohol) greater than 70% by volume. Take extreme care with handling bleach or other strong oxidizing solutions.
6. Flush the tap for an additional three minutes with cold water.
7. Reduce the water flow to a gentle flow, about the width of a pencil. 
8. Grasp the bottle cap along the top edge and remove carefully. Do not lay the cap down or put it in a pocket. Do not touch the inside of the bottle with your fingers. 
9. Hold the bottle in one hand and the cap in the other, fill the bottle until the water sample level is between the two lines on the bottle. From a side view, the water sample level in the center of the bottle must be above the bottom (100 mL) fill line and below the top (120 mL) line. If you overfill the bottle, pour off any excess water to get the water sample level between the two lines.
   • Do not change the water flow once you start filling the bottle.
   • Hold the bottle so there is nothing obstructing the water flowing from the tap and entering the bottle. Take care not to contaminate the sterile bottle or cap with your fingers or permit the faucet to touch the inside of the bottle.
   • If there is less than 100 mL of water in the bottle, or the water level is above the 120 mL line, the sample will not be tested. 
10. Place the cap on the bottle and twist it down firmly to prevent leaks during shipping.
11. Using waterproof ink, complete the Environmental Sample Collection Form (sample form) with the necessary collection information. 
    • There must be one sample form for each sample bottle. 
    • Be certain the Sample Type, Sample Collection Point ID, Date, Time (using 24-hour clock), PWS Name and ID Number are correct and the Bottle Number on the sample form matches the number on the side of the bottle. 
    • If your system is disinfected with chlorine or chloramines, provide the appropriate disinfectant residual(s) (Free Chlorine and/or Total Chlorine) on the sample form. 
    • If the sample collection point ID is different from what is specified on your sample siting plan or sample collection schedule, provide an explanation for discrepancy on a sampling log.
12. Make a copy of each completed sample form for your records (recommended).

Shipping Instructions

1. Place the completed sample form and corresponding sample bottle inside a box.
2. Seal the box with the mailing label provided. 
3. Drop off the sample(s) with your chosen courier to deliver the sample(s). Plan accordingly to be certain the sample(s) reach the laboratory within 30 hours of collection, as required. 
   • If you use the Missouri Department of Health and Senior Services' Courier Services, be sure to drop off the sample(s) by 10:30 a.m., the same day as collected, at any courier pickup location.​​ The Department of Health and Senior Services also provides a printable Courier Drop off Locations and Times list.
   • If you choose to use the U.S. Postal Service, the Missouri Department of Natural Resources recommends you use Priority Mail or faster to mail water samples. Contact the Missouri Department of Natural Resources’ Public Drinking Water Branch for more information.

Sample Results

• For systems using the State Public Health Laboratory, sample results are available within four to five days in Drinking Water Watch.
• For systems using an independent laboratory, contact the lab for sample results. Systems using independent laboratories are responsible for ensuring the sample results are submitted to the Missouri Department of Natural Resources. Complete a Microbiological Analysis Report MO 780-0438 and submit it to the department as soon as the water system’s monthly monitoring is completed, but in no case later than the 10th of the month following the month for which monitoring was performed.

Total-coliform Positive Notification

Sometimes despite taking all the precautions and following the sample collection procedures, you may receive notification that a routine sample is total-coliform positive.

• If using the State Public Health Laboratory, you would receive notification from the Missouri Department of Natural Resources regarding the coliform-positive routine sample. You will also be given specific instructions to collect a set of three repeat samples for each coliform-positive routine sample, according to your sample siting plan. 
  • Collect repeats from the original routine sample location, upstream and downstream locations within five service connections, or from approved alternative repeat sites, or approved locations specified in a standard operating procedure according to the sample siting plan. 
  • Groundwater systems with well(s) that are not provided 4-log virus inactivation and not conducting compliance monitoring under the Ground Water Rule are also required to collect a source water sample at an approved location before treatment from each well in service at the time of collecting the coliform-positive routine sample.
• If using an independent lab for bacteriological analysis, the system is responsible for collecting the necessary repeat samples and triggered source water samples, if required under the Ground Water Rule, within 24 hours of the coliform-positive sample notification. Not all independent laboratories notify the department of a coliform-positive sample until the next month.

Assessment Notification

The Missouri Department of Natural Resources will notify the system when an assessment is required to be conducted. 

• Level 1 Assessment: The system exceeds the treatment technique trigger for the first time within the last 12 months. The system conducts the assessment, completing the Revised Total Coliform Rule Level 1 Assessment MO 780-2638 and submitting it to the appropriate department Regional Office.
• Level 2 Assessment: The system exceeds the treatment technique trigger for a second time or more within the last 12 months, or the system exceeds the E. coli Maximum Contaminant Level. The department’s Regional Office staff will conduct the assessment. 

A system exceeds the treatment technique trigger if the following occur:

• A system serving a population of 1,000 or less has two or more total coliform-positive samples in a monitoring period
• A system serving more than 1,000 has a number of positive samples exceeding 5% of compliance samples taken in a given monitoring period
• Any system fails to collect all the required repeat samples within 24 hours of notification or within a department specified timeframe.

The purpose of an assessment is to look for and identify any sanitary defects that may have caused the contamination. The system must take corrective action to any sanitary defects discovered within 30 days of triggering the assessment or within the department specified timeframe.