VOC Sampling Instructions



Please read the following instructions carefully before sampling.  Improperly collected samples will result in increased cost to the water system.


Sample Kit Contents


·        1 refrigerant pack

·        1 40-mL vial labeled “Field Blank” and dated (The field blank serves as an indicator of contamination which may occur during sample transport or storage.  Therefore, this vial must not be opened and must always travel with the samples.)

·        2 40 mL vials for each source to be samples (These vials each contain 25 mg of ascorbic acid the must not be rinsed out during sample collection.)

·        2 red-capped 2 mL vials containing inserts filled with 2 drops of 1:1 Hydrochloric Acid (HCl).  CAUTION: Hydrochloric acid is corrosive.  If spilled on skin or clothes rinse with large quantities of water immediately.  Handle with care and wash hands when finished collecting samples.

·        Water sample Information form for each source to be collected




1)      All samples should be collected after treatment and before the distribution system (representative of the overall source)

2)      Use the same collection point each time you sample

3)      Remove any potentially contaminating devices such as filters, screens, aerators and vacuum breakers from the sampling tap.

4)      Open the tap and allow water to run (at least 3 minutes) until it reaches a constant temperature.

5)      Reduce the flow to a thin steady stream (the thickness of a pencil)

6)      Fill 2 vials from each source at the same time and under the same conditions.  Avoid agitation of the sample whiled filling.  Allow the stream of water to gently flow into the vial just to overflowing.



7)      After filling, transfer the complete contents, including insert, of one of the red-capped 2 mL vialss into each 40-mL vial.

8)      If necessary, gently add more water so that the sample vial looks like the illustration to the right.

9)      Carefully place the cap onto the vial.  The shiny side of the Teflon cap liner should be face down in contact with the water sample.  Tighten down the cap securely.

10)  Check for trapped air by inverting the vial and looking to see if any air bubbles are present.  If any air bubbles are present, gently add more water and repeat step 9.  When you are sure the vial is properly filled, shake vigorously.

11)  Label each vial with the DOH source number and your name for that source.  EXAMPLE: S01, Well #1


After Sample Collection:


1)      Place vials in the shipping container with the frozen refrigerant pack and the field blank.  Place the insulating material between the vials and the refrigerant pack.  Put the red-capped vials back into the container.  If you are not going to return the sample to the laboratory immediately upon returning from the collection site, place your samples in a refrigerator and the refrigerant pack back in a freezer.

2)      Complete the Water Sample Information form for each source collected.  Indicate the exact time, date, and location where the sample was collected.

3)      Write the correct System ID number, Group type (A or B) and DOH source number in the spaces provided on the Water Sample Information form.




When the forms are completed and you are ready to ship, follow the instructions above to again place samples in the cooler and then ship to the laboratory.  Twiss Analytical Laboratories, Inc. courier or UPS is satisfactory for shipping.  (Call to arrange courier service).  ALL SAMPLES MUST BE RECEIVED AT THE LABORATORY PRIOR TO 4:00 P.M. ON FRIDAY OF THE WEEK IN WHICH YOU SAMPLED.


Questions you have regarding drinking water regulations, system monitoring requirements or your particular system ID number and source numbers should be directed to the regional contacts listed on the Water Sample Information form.  Please contact Twiss Analytical Labs at (360) 779-5141 if you have any questions.