• Suspected Case Investigation.  Optimal sensitivity is desirable in the context of a case investigation; therefore, two samples, water and swab, should be collected from the same water outlet(s) in the immediate environment of a suspected case. 
  • Routine Monitoring. For routine environmental surveillance, one sample, either swab or water (or a combination of the two), of an outlet is acceptable. 
  • Post-disinfection Monitoring. Ongoing surveillance for monitoring the efficacy of disinfection efforts should include previously positive locations for follow up testing. 

Potable Water

  1. Fill out SPL Chain of Custody
  2. Use waterproof pen to label bottle and swab with sample location, description, and date.
  3. Swab collection:
    a) Remove aerator if present.
    b) Moisten the outlet by turning on the hot water–briefly.
    c) Insert swab into faucet opening rotating four times against the inner surface as it moves up into the opening (for shower head, rotate swab over entire surface of showerhead four times).
    d) Replace swab in transport tube.
  4. Water collection:
    a) Turn on hot water and immediately fill the bottle.
    b) Close bottle and invert to mix the sodium thiosulfate neutralizer.
  5. Repeat steps 2–5 with next sample location.

Hot Water Storage Tanks

  1. Open the drain valve at the base of the heater or tank and immediately fill bottle.
  2. Let the water continue to drain for 15–30 seconds to flush out residual water within the drain pipe.
  3. Fill a second sample bottle.
  4. Submit both samples, labeled Immediate and Post Flush.

Note: Swabs are not considered an appropriate sample for hot water tanks.

Cooling Towers

Submerge open bottle just under the surface of water to obtain approximately 120 ml of sample.

Note: Swabs are not considered an appropriate sample for routine testing of cooling towers.

Ice Machines

The ice is processed in the lab after allowing it to melt and is concentrated by filtration. Two or three sample bottles of ice are needed for adequate melted volume. Use SPL bottles to scoop up ice. If a water dispenser is part of the machine, collect the water as you would from any faucet: turn on the faucet and immediately fill the sample bottle. 

Note: A swab of the faucet opening can also be collected and is recommended if assessing the outlet as a source of infection during a case investigation.


  1. Ship the same day samples are collected for receipt in laboratory for delivery within 24 hours (recommended) and not to exceed 48 hours.
  2. Samples can be sent at room temperature or refrigerated (2–8° C) overnight, if necessary.
  3. Place bottles in box with insulated liner.
  4. Place completed Chain of Custody form in plastic document holder and pack in box.
  5. Ship overnight Monday–Thursday only: Special Pathogens Laboratory, 1401 Forbes Avenue, Suite 401, Pittsburgh, PA 15219

Questions? Call 412-281-5335