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Cleaning & Prevention of Legionella Bacteria in Air Conditioners & Heat Pumps InspectAPedia®  -     Cleaning air conditioning condensate trays Cleaning air conditioning cooling towers Legionella, mold, and other pathogenic risks Use of chlorine, bromine, inspections, cleaning Contributions and critique are invited

This website discusses Legionella bacteria in air conditioners, how to clean air conditioning systems, Legionnaire's disease prevention & cleaning suggestions for air conditioning equipment and condensate trays, including condensate piping, traps, drains, condensate pumps, and concerns for mold, Legionella bacteria, and other hazards associated with air conditioning systems, cooling towers, and evaporative coolers.

This is a chapter of our full document describing the inspection, maintenance, and repair of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.

© Copyright 2010 Daniel Friedman, All Rights Reserved. Information Accuracy & Bias Pledge is at below-left. Use links at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

CONDENSATE TRAY CLEANING - Cleaning suggestions for A/C System Condensate Systems

Should we disinfect cooling system equipment or condensate trays?

Should we be putting bromide or chlorine tablets in our condensate trays to keep bacteria from growing?

If we should be, then do we need to alternate bromide with chlorine on some type of frequency to prevent development of resistant bacteria?

We're discussing condensate trays from mechanical equipment like heat pumps, fan coil units and air handlers with AC coils.

These pieces of equipment have condensate trays which are then drained through a small pipe, usually clear, but not always, with a trap in it, to a drain.

These condensate trays have some standing water in them when the AC is functioning. Should these condensate trays be treated with an algaecide of some sort?

There are risks beyond mold and algae, in particular Legionella bacteria (legionnaire's disease) which can have an alarmingly high mortality rate, and also potential hazard sources such as biofilms that can include other bacterial and maybe other pathogens. However the risk of formation of problem levels of mold, bacteria, or other pathogen is probably not the same across all buildings nor types of equipment, and much of the risk may depend on installation and maintenance details at individual installations.

Particularly in climates with a high humidity and a heavy cooling load, and depending on details of the design and installation of the air handler unit and duct work, there is risk of blowing pathogen-contaminated water droplets downstream inside the air conditioning duct work and thus exposing building occupants.

With rooftop-mounted cooling units such as cooling towers using water, conditions may be still more attractive for growth of pathogens and there is some risk of movement of pathogens out of the cooling equipment to people located nearby and downwind from the equipment, even if they are outside the building which the equipment actually serves.

While I am not expert on this topic I have collected and provide here some key information and opinions to help sort out these questions. Use the links at page left to read additional details on this topic including recommended cleaning procedures and details of the Legionella hazard in air conditioning systems, humidifiers, etc.

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Technical Reviewers & References

• InspectAPedia.com^® - Daniel Friedman
• Critique, contributions wanted: Contact Us to suggest corrections or additions to articles at this website, and if you wish, to receive online listing and credit as a contributor. Particular thanks are due to the many experts and also consumers who read and critique technical articles at InspectAPedia.com.
• Thanks to remaining contributors/references who are listed just below

Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.

AIR CONDITIONING SYSTEMS
AIR CONDITIONER BTU CHART
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR CONDITIONER NOT WORKING
AIR FILTERS for HVAC SYSTEMS
AIR HANDLER UNITS
  ADDING A/C: RETROFIT SIZING
  BLOWER LEAKS, RUST & MOLD
  COOLING COIL DEFECTS
  DIRTY A/C BLOWERS
    Leaks, Rodents In Air Handlers
    Mold Growth in Air Handlers
BACKUP HEAT for HEAT PUMPS
BLOWER DOORS & AIR INFILTRATION
BOOKSTORE - Air Conditioning "How To" Books
CLEANING & Legionella BACTERIA
  Should we disinfect
  Wisconsin Protocol for Cleaning A/C
  Legionella sp. Health Concerns
  What are Legionella
  Where do Legionella sp. occur?
  Recommended Level for Legionella sp.
  How When to Test for Legionella sp.
  Legionnaires' Disease Information from CDC
COMPRESSOR & CONDENSING COIL
CONDENSATE HANDLING
  DRIP TRAY DEFECTS
  CONDENSATE LEAKS
  CONDENSATE PUMPS
  CONDENSATE DRAINS
  CONDENSATE TRAY CLEANING
CONTROLS & SWITCHES
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
  DAMAGED COOLING COIL
  DIRTY COOLING COIL
  DIRTY COIL CLEANING PROCEDURES
  FROST BUILD-UP
DATA TAGS on AIR CONDITIONERS
COMBUSTION GASES & PARTICLE HAZARDS
COMBUSTION PRODUCTS & IAQ
DEFINITION of Heating & Cooling Terms
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DUCT SYSTEMS
DUCTS - Asbestos
DUCT SYSTEM DEFECTS
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCTS, Asbestos Transite Pipe
DUST FROM HVAC?
ENERGY SAVINGS in BUILDINGS
EVAPORATIVE COOLING SYSTEMS
FAN AUTO ON Thermostat Switch
FAN CONVECTOR HEATERS - HYDRONIC COILS
HEAT LOSS (or GAIN) in BUILDINGS
HUMIDITY LEVEL TARGET
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS
LOST COOLING CAPACITY
MOTOR OVERLOAD RESET SWITCH
OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES
REPAIR GUIDE for AIR CONDITIONERS
REPAIR & DIAGNOSTIC FAQs for A/C
REFRIGERANTS
SEER RATINGS & OTHER DEFINITIONS
SYSTEM OPERATION
SWAMP COOLERS
THERMOSTATS
THERMOSTATIC EXPANSION VALVES
CRITICAL DEFECTS
Air Conditioning "How To" Books

• Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects" section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and home inspection educator.
• http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_7.html is OSHA"s technical manual re Legionnaire's disease US EPA Safe Drinking Water Hotline: 800-426-4791
• "Legionella in NY - How to Conduct a Legionella Risk Assessment", Mark Hodgson, LSC, Naperville IL & Diane Miskowski, MPH, EMSL Analytical, Inc., Westmont NY, Crown Plaza, White Plains, 8 May 2007. Course description: "Guidelines for the control of Legionella in critical care hospitals in New York have been in place for two years. In October 2006, these guidelines were extended to include nursing homes and long term care facilities. Join us for this 8 hour seminar to learn all you need to know to conduct a Legionella health risk assessment, control it in your facility, and remediate it. This course will describe the ecology of the [Legionella] organism, the epidemiology of the disease [Legionnaire's disease], a discussion of some recent outbreaks, and the proper sampling methods and analysis of the bacteria. A significant amount of time will be spent discussing how to actually perform a Legionella risk assessment, and an overview of cooling towers and potable water system design and how that contributes to growth of the [Legionella] organism. Discussion will include where Legionella can be found in the engineered environment, and the use of biocides and other controls."
• Thanks to Craig Balchunas, AHI Accurate, LLC., a home inspection firm in Hyde Park, NY. - (800) 360-3998
• "Legionella", a public information poster provided free by LA Testing, an California environmental testing lab - www.LATesting.com.

Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• Principles of Refrigeration, R. Warren Marsh, C. Thomas Olivo, Delmar Publishers, 1979
• "Air Conditioning & Refrigeration I & II", BOCES Education, Warren Hilliard (instructor), Poughkeepsie, New York, May - July 1982, [classroom notes from air conditioning and refrigeration maintenance and repair course attended by the website author]
• Refrigeration and Air Conditioning Technology, 5th Ed., William C. Whitman, William M. Johnson, John Tomczyk, Cengage Learning, 2005, ISBN 1401837654, 9781401837655 1324 pages
• Carson Dunlop, Associates, Toronto, have provided us with (and we recommend) Carson Dunlop Weldon & Associates' Technical Reference Guide to manufacturer's model and serial number information for heating and cooling equipment ($69.00 U.S.).
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