Legionella Sampling Instructions


Use sterile bottles (available from the lab) supplied with sodium thiosulphate.

Recommended sampling volume:

  • 100-250 mL for cooling towers,
  • 500-1000mL for potable water.

For potable water sources, it is recommended to take two samples per site; a pre flush and a post flush. Allow the water to run for 2 minutes before taking a post flush sample.


Swabs (available from the lab) are indicated for sampling the biofilm at the bottom of cooling towers, around faucets, showers, at the bottom of water fountains. Use the swab supplied by the lab as follows:

  1. Remove the sterile swab from the plastic holder and sample the area of concern.
  2. Place back the swab in its holder.
  3. Make sure that the swab is tightly secured in the pouch.
  4. Bend and press the red tab at the upper section end to allow the diluent to flow down to the lower pouch section on to the swab.

General Precautions

  • Use a water resistant marker to label the sample.
  • Place the sample immediately in a cooler box (polystyrene foam boxes work well) with an ice pack.
  • Ensure that the sample is not in direct contact with the ice pack by using some packaging material in between.
  • Submit the samples to the lab within the shortest delay, preferably within 48 hours. As per ISO 11731 method, the holding time can be extended to 5 days for samples coming from remote areas provided that these are kept in good cooling conditions.
  • It is preferable to sample early in the week preferably by Wednesday to ensure that these reach the lab by Friday at latest.
  • The TAT is 10 days; preliminary result may be available after 6 days for high counts of Legionella.
  • All samples must be submitted with a duly filled chain of custody (COC) form; it is preferable to send an electronic copy of the COC directly to the lab. Otherwise put the COC in a Ziploc bag in the cooler box.

qPCR Analysis for Water and Swab Samples

  • Recommended sampling volume; cooling towers- 200 mL, other sources- 500 mL.
  • The instructions (bottles, swabs and precautions) for Legionella analysis by culturing above also apply for qPCR analysis ISO 12869 method.
  • Specify qPCR analysis on the COC, TAT is generally 24 hours.