When to Test for Legionella

You do not usually need to test for Legionella if your temperatures are right. But you should test when:

• Temperatures are wrong a lot of the time
• The system has been changed
• After cleaning and disinfecting (wait 3-7 days)
• Someone has caught Legionnaires' disease
• You are in a hospital or care home

What You Need

• A clean 1 litre sample bottle (it must have sodium thiosulphate inside - this stops the chlorine)
• Gloves
• A marker pen
• Chain of custody forms
• A cool box with ice packs (keep samples at 2-8 degrees C)

How to Take the Sample

1. Pick the right tap - Use a normal tap, not a mixer valve. If you can, sample before the mixer.
2. Remove attachments - Take off shower heads, aerators, and flexible hoses.
3. Put on gloves.
4. Label the bottle - Write the date, time, where it is, tap name, and your name.
5. Run the water for 2-3 seconds only - Do NOT flush for a long time. Flushing washes away the bacteria and gives a false low result.
6. Fill the bottle - Hold it at an angle so you do not touch the tap. Fill to the neck but leave some space at the top.
7. Cap it right away and tip it gently to mix.
8. Put it in the cool box with ice packs. Do NOT freeze it.
9. Fill in the chain of custody form.
10. Get it to the lab within 24 hours.

Understanding the Results

| Result | What It Means | What to Do | |---|---|---| | Under 100 CFU/L | Good | Keep doing what you are doing | | 100-1,000 CFU/L | Not great | Review your checks, clean if needed, test again | | Over 1,000 CFU/L | Bad | Clean and disinfect right away, test again 3-7 days after | | Over 10,000 CFU/L | Very bad | Consider shutting down the system, disinfect, find the cause |