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This air conditioning repair article discusses the inspection, diagnosis, and repair of air conditioning condensate drainage systems, including condensate leaks, condensate piping, traps, drains, condensate pumps, and the detection and hazards of air conditioning system condensate leaks in buildings.

Condensate leak water health and safety concerns are also reviewed. This document describes the inspection of residential air conditioning systems (A/C systems) to inform home buyers, owners, and home inspectors of common cooling system defects.

At AIR CONDITIONING & HEAT PUMP SYSTEMS, the major components of an air conditioning system are described, and at A/C COMPONENTS sketches and photographs are provided, and common defects for each component are listed along with visual or other clues that may suggest a problem or probable failure of A/C components. Readers who need to clean or unclog a blocked or leaky overflowing A/C or heat pump condensate drain should see CONDENSATE DRAIN CLEAN & DE-CLOG.

Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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CONDENSATE HANDLING - Air Conditioning Condensate Handling Defects

Condensate leaks or discharge errors (such as the drips into the dog bowl and cooking pot in this attic) present several risks of ugly surprises in buildings.

Here are some inspection tips that can avoid a condensate leak or even a costly mold problem in the air conditioning system air handler, duct work, or in the building itself:

First locate and document where condensate discharge is carried

• a plastic line draining outside to an approved drain destination - see CONDENSATE DRAINS
• a floor drain
• a sump pit
• a hole in the floor
• a reservoir lift pump (CONDENSATE PUMPS) which pipes condensate to: (a properly connected building drain; something else)
• the pump exit line is taken to the house main waste line
• a dirt floor or crawl space (a bad idea, asking for mold or insect damage)

Look out for a missing condensate overflow pan: if there is no overflow pan under the air handler, especially in units installed on upper building floors or in an attic, when the condensate drain clogs or the condensate pump fails you can expect to have leaks into the building and possibly costly mold or water damage.

Look out for an improper condensate overflow pan drain connection: a condensate pan should have its own independent drain to an approved location. Otherwise, for example if it shares the main condensate drain pipe, you have not gained much protection. An alternative to a drain on a condensate overflow pan is the installation of a Float Switch on Condensate Tray that will turn off the system if water is detected. See CONDENSATE DRAINS.

Look for corrosion or water stains on floor surfaces around the equipment, at the condensate drip pan and at bottom of the "A frame" cooling coil, indicating that the drain may need cleaning and more important, indicating that the condensate is leaking out of the equipment or drains and not being carried to an acceptable disposal point.

Links below continue with detailed discussions of condensate handling components, defects, cleaning, maintenance, and repairs.

Periodic Inspection of the Air Conditioner Condensate Drain System - Some Suggestions

Question: how and when do we inspect the condensate drain?

I can't find a description of the method for inspecting the drain pipe leading out from the drain pan under the condenser coils.

I have been told that this pipe commonly blocks up and causes problems and that inspecting it is a part of a HVAC maintenance program. Would you describe for me, or maybe add to your site, how often and how this drain line should be inspected and maintained?

- R.B. Chattanooga, TN.,

Reply:

The condensate drain line, trap, and evidence of blockage, leaks, overflow, or improper piping should be part of annual air conditioning system service, or should be performed immediately if there is evidence of a condensate spill or leak. It only takes a quick look by an experienced service technician to see trouble. Here are some signs of trouble that a visual inspection of the condensate drain system might pick at an inspection:

• Visual inspection for obvious debris at opening to the condensate drain, inside the air handler
• Visual inspection for evidence of condensate overflowing out of or backing up in the air handler when it should be passing out the drain - such as is shown in our photo at left.
• Visual inspection for condensate backup or spillage such as presence of condensate in an overflow pan
• Tripping off of the float switch in the overflow pan if you have one
• Some condensate drains have a removable cap on the trap to inspect in and clean the trap - traps are usually where blockages occur
• Visual inspection of the entire drain line to see its routing - and to assure it's taken to a proper destination. Our photo at the top of this section above shows a crimped condensate drain pump line - we were a bit worried that with even the slightest additional movement in this soft flexible plastic tube (connecting the condensate pump to a nearby laundry drain) would prevent the pump from working properly.
• Failure of any condensate to come out of the exposed end of the condensate drain line when the A/C system has been running during hot, humid weather
• If a condensate pump is installed, overflow of condensate out of the pump housing
• Check out the articles listed below for more detail about each type of condensate drain system defect.

Questions & Answers about handling air conditioner and heat pump condensate

Question: Our heat pump spills water onto the floor. What's wrong and how do we fix it?

I have a question regarding our heat pump. Last summer it started leaking water. The system otherwise runs fine but we have to keep a bucket where the water comes out a rubber tube. This also does not catch all the water because the carpet still gets wet. There is no problem with heating this past winter. Is there a pump of some kind that needs to be replaced.- M.M.

Reply:

It sure sounds as if your heat pump when in cooling mode is leaking condensate into the building. When warm moist indoor air passes through the cooling coil, moisture is removed from the air as it cools, condensing into water that must be drained away to an acceptable location - a floor drain or in some areas outdoors onto the ground.

A condensate leak that spills into the building interior could be caused by any of several problems such as a clogged condensate drain line or if a condensate pump is used to lift condensate from a receiving container up to a building drain, the pump could be switched off or broken.

You need to first diagnose the cause of the problem. If it's just a clogged drain line, clearing the line can get things working again quickly and probably at little or no cost. If you are unfamiliar with the equipment or can't find the condensate handling system, or if a condensate pump is not working you probably need a service call by an HVAC expert.

Look through the articles found in the links at page left under CONDENSATE HANDLING for more details about different condensate handling problems, diagnoses, and repairs.

Watch out: in a good heat pump/air conditioner installation, the installers make provision to protect the building interior from condensate leakage should the primary condensate drainage system fail. Usually that's in the form of a condensate drip tray that is placed under the indoor air handler where the cooling coil is located (and where condensate is produced). If the condensate drain system fails and condensate begins to leak out of the equipment, the drip tray either takes condensate safely away to a drain by a separate drain line or it uses a switch that shuts down the equipment so that you know repairs are needed. Condensate that leaks into building carpets, ceilings, walls, risks formation of a costly mold contamination issue. So get this matter repaired promptly.

Question: Water blowing down my HVAC Supply Ducts, What Can I Do to Stop It?

Why is water blowing down my supply duct system? I have solved the freezing up problem, I don't have a drain problem!! I added refrigerant to solve the freezing up problem, but it is still blowing water down my supply line. How do I stop this?? - C.T.

Reply: Check the A/C system sizing, check for abnormal indoor humidity sources

If you are sure that the condensate drain is in fact draining, I don't know a simple in-air-handler fix for this problem - it's common in some humid areas such as Florida. I'd take a look at these next steps:

1. Check whether or not your A/C system is oversized for the space being cooled; a cooling system that is oversized will not dehumidify adequately and that leaves too much water in your building air
2. If #1 is not the issue, look for and fix sources of abnormal indoor moisture: leaks, failure to use bath and kitchen vent fans, particular lifestyle that puts lots of moisture into the air (cooking?); and consider some auxiliary dehumidification

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AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C COMPONENTS
A/C DATA TAGS
A/C - HEAT PUMP CRITICAL DEFECTS
A/C DIAGNOSTIC FAQs
A/C REFRIGERANTS
A/C TYPES, ENERGY SOURCES

AIR CONDITIONER BTU CHART
AIR FILTERS for HVAC SYSTEMS

AIR HANDLER / BLOWER UNITS
ANIMAL ALLERGENS / PET DANDER
ANIMAL ENTRY POINTS in buildings
ANIMAL ODORS IN buildings
APPLIANCE EFFICIENCY RATINGS
ASBESTOS IDENTIFICATION IN buildings

BACKUP HEAT for HEAT PUMPS

BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING

BOOKSTORE - Air Conditioning "How To" Books

CAPACITORS for HARD STARTING MOTORS
CAPILLARY TUBES
CHINESE DRYWALL HAZARDS
CIRCUIT BREAKER SIZE for A/C or HEAT PUMP
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 CONDENSER
CONDENSATE HANDLING
  DRIP TRAY DEFECTS
    Missing Condensate Overflow Pan
    Improper Condensate Drain Connects
    Float Switch on Condensate Tray
    Water in Condensate Overflow Pan
  CONDENSATE LEAKS
  CONDENSATE PUMPS
  CONDENSATE DRAINS
    Locations for Condensate Disposal
    Plumbing Code for Condensate Drains
    Improper Condensate Disposal
    Condensate Drains Connected to Vent Pipe
    Condensate Spills in Crawl Spaces
    Condensate Leaks Onto Heat Exchangers
    Condensate Disposal Outdoors
    Condensate Drains to Hidden Location
  CONDENSATE DRAIN CLEAN & DE-CLOG
  CONDENSATE TRAY CLEANING
CONTROLS & SWITCHES, A/C - HEAT PUMP
COOL OFF HEAT Thermostat Switch
COOLING CAPACITY, RATED
COOLING COIL or EVAPORATOR COIL
COOLING LOAD REDUCTION by ROOF VENTS
COMBUSTION GASES & PARTICLE HAZARDS
CONDENSATE HANDLING, A/C
CONDENSATION or SWEATING PIPES, TANKS

DATA TAGS on AIR CONDITIONERS
DEFINITION of Heating & Cooling Terms

DEHUMIDIFICATION PROBLEMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE

DIAGNOSE & FIX AIR CONDITIONER / HEAT PUMP
DUCT SYSTEM & DUCT DEFECTS
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST CONTAMINATION FROM HVAC?

EDUCATION, HVAC SCHOOLS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
ELECTRIC MOTOR OVERLOAD RESET SWITCH
ELECTRICAL POWER SWITCH FOR HEAT

ENERGY SAVINGS in buildings
EVAPORATIVE COOLING SYSTEMS
EVAPORATOR COIL or COOLING COIL
EXPANSION VALVES, REFRIGERANT

FAN, AIR HANDLER BLOWER UNIT
FAN AUTO ON Thermostat Switch
FAN, COMPRESSOR/CONDENSER UNIT
FAN CONVECTOR HEATERS - HYDRONIC COILS
FAN LIMIT SWITCH
FAN NOISES

FURNACES WARM AIR HEATING SYSTEMS

GASES, EXPOSURE, TESTING
  Carbon Dioxide - CO₂
  Carbon Monoxide - CO
  METHANE GAS SOURCES
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GAUGE, REFRIGERATION PRESSURE TEST

HEAT LOSS (or GAIN) in buildings
HEAT PUMPS

HUMIDITY LEVEL TARGET

INDOOR AIR QUALITY IMPROVEMENT GUIDE
INSPECTION LIMITATIONS
LEED GREEN BUILDING CERTIFICATION

LOST COOLING CAPACITY

MANUALS & PARTS GUIDES - HVAC
MOTOR OVERLOAD RESET SWITCH

NOISY AIR CONDITIONER / HEAT PUMP
NOISE / SOUND DIAGNOSIS & CURE
  Air Leak Noises
  AIR CONDITIONING & HEAT PUMP NOISES

OPERATING COST
OPERATING DEFECTS
OPERATING TEMPERATURES

PORTABLE ROOM AIR CONDITIONERS
PRESSURE READINGS, REFRIGERANT

REPAIR GUIDE, AIR CONDITIONERS / HEAT PUMPS
REPAIR & DIAGNOSTIC FAQs for A/C

REFRIGERANTS
  GAUGE, REFRIGERATION PRESSURE TEST
  REFRIGERANT CHARGING PROCEDURE
  REFRIGERANT DRIERS & FILTERS
  REFRIGERANT LEAK DETECTION
  REFRIGERANT LEAK REPAIR
  REFRIGERANT METERING DEVICES TEVs
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  REFRIGERANT PIPING & DISTANCES
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RETROFIT SIZING for A/C or HEAT PUMPS

SEER RATINGS & OTHER DEFINITIONS
SOLAR ENERGY SYSTEMS
SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS
SWAMP COOLERS
SYSTEM OPERATION

THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
CRITICAL A/C or HEAT PUMP DEFECTS

• Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. Thanks to Alan Carson and Bob Dunlop, for permission to use illustrations from their publication, The Illustrated Home which illustrates construction details and building components. Carson Dunlop provides home inspection education including the ASHI-adopted Home Inspection Training Program (home study course), publications such as the Home Reference Book, report writing materials including the Horizon report writer, and home inspection services. Alan Carson is a past president of ASHI, the American Society of Home Inspectors.
• Thanks to reader RB in Chattanooga TN for discussing inspection procedures and inspection frequency for air conditioning condensate drain line systems - October 2010

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

• Our recommended books about building & mechanical systems design, inspection, problem diagnosis, and repair, and about indoor environment and IAQ testing, diagnosis, and cleanup are at the InspectAPedia Bookstore. Also see our Book Reviews - InspectAPedia.
• 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.).
• Air Conditioning Inspection, Diagnosis, Repair, Efficiency all the basics for home owners, inspectors, new repairmen
• Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard
• Asbestos HVAC Ducts and Flues field identification photos and guide
• Fiberglass: Indoor Air Quality Investigations: Fiberglass in Indoor Air, HVAC ducts, and Building Insulation
• ...