Copper-silver ionization is a disinfection method that is used to eradicate Legionella from hot water recirculating systems. Disinfection with ionization occurs when the positively charged copper and silver ions released from the ionization system bind to the negatively charged cell wall of Legionella causing cell death. Ion concentration should be monitored to document that effective levels have been achieved and to avoid excess ion levels.

Target Range
Suggested target ion range for Legionella control: Copper:  0.20–0.80 mg/L; Silver:  0.01–0.08 mg/L

EPA Limits 

  • Copper is listed on the EPA’s Primary Metal contaminant list not to exceed 1.3 mg/L and is an enforceable standard.
  • Silver is listed on EPA’s Secondary Metal Contaminant list not to exceed 0.10 mg/L and is not an enforceable standard.
  • Choosing the right sampling sites is important to ensure that the proper levels of copper and silver ions are being distributed to the entire water system so that maximum disinfection will be achieved.  

Test Method 

EPA 200.8; Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma-Mass Spectrometry

Turn Around Time

 7–10 days

Test code


Suggested Sampling Sites 

  • The immediate water after it passes through the electrode cell on the supply side of the heating element or first distal outlet in the hot water system
  • Return line or last distal outlet before the water passes through the electrode cell
  • Distal outlets representing the midpoint of disinfection loop


  1. Complete the Chain of Custody Test Request form.
  2. Use waterproof pen to label bottles with sample location, description, and date.
  3. Turn on hot water and wait until the hot water temperature reaches its maximum and fill the bottle (≥120 mL).  Sample should be clear, avoid sediment. 
  4. Place bottles in box with insulated liner.

Sample transport 

Overnight delivery is recommended but not required. 

  1. Ship the same day samples are collected
  2. Place bottles in box with insulated liner.
  3. Place completed Chain of Custody Test Request form in plastic document holder and pack in box. 
  4. Ship overnight Monday–Thursday only to: Special Pathogens Laboratory, 1401 Forbes Avenue, Suite 401, Pittsburgh, PA 15219

Questions? Call SPL at 412-281-5335