How to Take a Water Sample
Water may appear clear and pure, but water from wells
or other sources may contain dissolved minerals and other
substances. Generally, ground water provides a good
supply of safe water, that doesn't need much treatment.
If you are a private well owner, you need to test your
water supply to insure the well provides safe, high
quality water.
With the advice of your county Health Department or
Cooperative Extension office, decide what tests are
needed for your water supply. After selecting the tests,
choose a lab to test the samples.
Steps required for taking a water sample will vary
for different tests. Timeliness and cleanliness are
important when collecting any water sample. Use the
sterile collection bottles the lab sends you and not your
own bottles to take a sample. Labs often will only accept
samples taken in their collection bottles. Also complete
all the forms the lab requires to process the sample.
A water sample needs to be submitted to the lab
within 48 hours of collection. In some cases it must be
kept cold prior to testing. Care must be taken to prevent
anything but the water from contacting the inside of the
bottle or the cap. Contaminants are often present in
small amounts. Careless sampling prevents accurate test
results.
General Procedures
For most water tests, follow these steps when
collecting a sample:
- Take the sample close to the pump, before the water
goes through a treatment system.
- Do not take the sample from a swing-type faucet.
Inspect the faucet for leaks. Select another faucet if
there is leaking.
- Remove the aerator.
- Disinfect the faucet with bleach or a flame.
- Run the water several minutes to clear the line.
- Take the sample midstream. Do not touch the sides of
the collection bottle, the opening or inside of the cap.
- If needed, store the sample in the refrigerator before
taking to the lab.
- Submit the sample within 48 hours of collection.
- Transport the sample in a cooler or ship in an
insulated container.
Some tests, such as lead, require the water stand in
the pipes overnight before taking a sample. Again, follow
the instructions provided by the lab or your Health
Department.
Testing for Volatile Organic Chemicals
When collecting a sample to be tested for volatile
organic chemicals these additional steps should be
followed:
- Reduce water flow to prevent excess air in the sample.
- Remove all air from the collection bottle by filling it
to almost overflowing. Again, timeliness and cleanliness
are extremely important to prevent false results.
Testing for Pesticides
Samples for pesticide testing must be taken so they
will not deteriorate or become contaminated before
reaching the lab. Contact the lab testing the sample for
complete instructions and a collection kit. Specific
steps needed when testing for pesticides include:
- Collect the sample only in the amber colored bottle
provided. The dark glass prevents light from degrading
the sample.
- Cap the bottle with the Teflon coated lid. The special
lid prevents false positive results caused by certain
plastics.
- Keep the sample refrigerated, preferably 35 degrees to
38 degrees, and submit it to the lab within 48 hours. If
shipping the sample, pack the sample in ice and ship in a
Styrofoam or other insulated container.
Test Results
If test results show an unacceptable contamination
level you should seek the advice of a professional. In
most cases a second test will be taken before
recommending possible treatments.
Test Records
Keep a record of your water tests. The record should
include the date and the test results. Comparing recent
test results to previous test results might point out
problems you may not have noticed. Water test records are
often needed for property sales. Records also support
damage claims from outside contamination, such as from
chemical spills or leaks.
For Further Information: for further information on
water testing or possible contamination suspected in your
area, contact your local Health Department or county
Cooperative Extension office.