Florida Department of Environmental Protection
Small Water System’s Guide to Sampling Coliform Bacteria
If you correctly collect your samples and ship them to the laboratory, sample collection is a relatively simple task
that does not take very much time. If you follow incorrect procedures, you may contaminate an otherwise good
sample (which will require the collection of additional samples, and may lead to drinking water quality violations
and public notification) or you may have to replace a sample that could not be analyzed by the lab.
Collect your routine sample early in the compliance period so there will be enough time to collect replacement
samples if the original sample is damaged in transit or cannot be analyzed in the lab.
Ensure that the sampling tap is clear of any debris.
Open the sampling faucet full and flush it for about 20-30
seconds. (If the faucet has an aerator or strainer, remove it
Adjust the water flow to a slow, even stream -- about the diameter of a pencil. Allow the water
to run for about 3 or 4 minutes (5 or 6 minutes if the faucet was not flamed in Step 2) to assure
that the water is flowing from the water main, not the building plumbing. While the water is
running, make sure the sample report form is filled out properly.
Using the DPD colorimetric test kit, analyze for residual chlorine and record the results on the
Use only the sample container supplied by the laboratory that will analyze the sample -- this may
be a glass or plastic bottle, but most likely it will be a plastic bag such as Whirl-Pack®. The
container is sterilized and contains a solution or tablet of sodium thiosulfate to neutralize any
residual chlorine that may be present in the sample. Do not rinse or boil the container, place your
finger in it, or otherwise tamper with it.
Open the sample bag or bottle only when you are ready to collect the water sample.
Using a bag: Follow the instructions that came with the bag for opening the bag and holding it.
Keeping the water flow at a slow, even stream, fill the bottle just to the fill line
or shoulder of the bottle or, if using a bag, fill to the white line. You must Florida Department of
collect at least 100 milliliters (mL) of water or the sample cannot be analyzed. Small Water System’s Guide to
Be sure there is an airspace above the water in the bottle or in the bag. Do not Sampling Coliform Bacteria
let the container overflow, and avoid splashing water on the outside of the Page 2
Using a bag: Immediately close the bag by pulling the wire tapes to straighten
them. Whirl the bag around the wires three or four complete revolutions to seal
the bag tight. There should be a pocket of air inside the bag. Turn the ends of the tapes inward,
opposite the fold, and twist the wire tape ends together. Be careful to turn the wire ends so the
bag will not be punctured during transit.
Complete the sample report form and transport the sample to your laboratory or mail it to the
state laboratory. If you are using the state laboratory, take the sample just before mailing, or keep
the sample iced or refrigerated between 1 and 5 C (33 and 41 F) until it is ready to be mailed.
The sample must be received at the state lab within 30 hours of the time it was collected for it to
be valid for analysis. Samples received between 30 and 48 hours from the collection time will be
analyzed, but the data may be questionable. Check with your local post office to see when mail
is picked up and time. If you have problems getting your samples to the lab by mail, try a
package delivery service or a courier service, or try delivering them to the lab yourself.
Note: The State Lab accepts samples only on weekdays; samples arriving at the lab on Saturday
or Sunday will not be processed until Monday, by which time they will no longer be valid.
Samples more than 48 hours old will not be analyzed; they will be discarded and you will be
directed to collect a replacement sample.
The list below contains locations that should be avoided when Florida Department of
sampling: Small Water System’s Guide to
Sampling Coliform Bacteria
•Locations with separate storage tanks (such as building with fire protection
system storage tank and sprinkler system)
•Buildings with "point-of-entry" water treatment system (such as water
softener, whole-house water filter, single-home chlorinator)
•Buildings with newly-installed plumbing
•Faucets with aerators or strainers, unless the aerator or strainer is removed before
•Faucets with swivel-type connection (such as a kitchen faucet)
•Faucets with water filter or "water purifiers" attached
•Leaky faucets that allow water to run along outside of the faucet
•Faucets with vacuum breaker backflow preventer attached directly to outlet
•Hot water faucets
•Hoses (garden hose, slop-sink hose)
•Fire hydrants or freeze-proof yard hydrants
If you need help selecting sampling sites, call the Florida Department of Environmental Protection at
CERTIFIED LABS IN THE Florida Department of
Small Water System’s Guide to
NORTHWEST DISTRICT Sampling Coliform Bacteria
Department of Health Lab, Pensacola
Department of Health Lab, Jacksonville
If you have any questions, please call the Potable
Water Section of the Department of Environmental
Protection, Pensacola, at (850) 595-8300.