Question? Just ask us!
Free Encyclopedia of Building & Environmental Inspection, Testing, Diagnosis, Repair
InspectAPedia ® Home
AIR CONDITIONING & HEAT PUMP SYSTEMS
A/C - HEAT PUMP CONTROLS & SWITCHES
AIR CONDITIONER COMPONENT PARTS
AIR CONDITIONER TYPES, ENERGY SOURCES
AIR FILTER EFFICIENCY
AIR FILTERS, FIBERGLASS PARTICLES
AIR FLOW MEASUREMENT CFM
APPLIANCE DIAGNOSIS & REPAIR
APPLIANCE EFFICIENCY RATINGS
BLOWER DOORS & AIR INFILTRATION
BLOWER FAN CONTINUOUS OPERATION
BLOWER FAN OPERATION & TESTING
BOOKSTORE - Air Conditioning "How To" Books
CAPACITORS for HARD STARTING MOTORS
CLEANING & Legionella BACTERIA
CHINESE DRYWALL HAZARDS
CONDENSATION or SWEATING PIPES, TANKS
DEFINITION of HEATING & COOLING TERMS
DEW POINT CALCULATION for WALLS
DEW POINT TABLE - CONDENSATION POINT GUIDE
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DUCTS - Asbestos
DUCT INSULATION, Asbestos Paper
DUCT INSULATION for SOUNDPROOFING
DUCT SYSTEM & DUCT DEFECTS
DUCT SYSTEM NOISES
DUCTS, Asbestos Transite Pipe
DUST, HVAC CONTAMINATION STUDY
ELECTRIC MOTOR OVERLOAD RESET SWITCH
EVAPORATIVE COOLING SYSTEMS
FAN LIMIT SWITCH
GAS EXPOSURE EFFECTS, TOXIC
GAS DETECTION INSTRUMENTS
HEAT LOSS (or GAIN) in buildings
HEAT LOSS (or GAIN) INDICATORS
HEAT LOSS R U & K VALUE CALCULATION
HEATING SMALL LOADS
INSPECTION CHECKLIST - OUTDOOR UNIT
INSPECTION LIMITATIONS, A/C SYSTEMS
LEED GREEN BUILDING CERTIFICATION
LOST COOLING CAPACITY
LOW VOLTAGE TRANSFORMER TEST
MOTOR OVERLOAD RESET SWITCH
MOLD in AIR HANDLERS & DUCT WORK
OPERATING COST, AIR CONDITIONER
OPERATING DEFECTS, AIR CONDITIONING
REPAIR GUIDES A/C / HEAT PUMP
REPAIR & DIAGNOSTIC FAQs for A/C
THERMOSTATS, HEATING / COOLING
THERMOSTATIC EXPANSION VALVES
WATER COOLED AIR CONDITIONERS
WINDOW / WALL AIR CONDITIONERS
WINDOW / WALL A/C SUPPORTS
A/C condensate drains & pumps: codes, installation, leaks, clogs, connections, troubleshooting & repair: this air conditioning repair article discusses the inspection and repair or un-clogging of air conditioning condensate systems, including Air Conditioning condensate drains, condensate pumps, and their proper installation as part of our review of condensate piping, traps, drains, condensate pumps, and the detection and hazards of air conditioning system condensate leaks in buildings.
Condensate leak health and safety concerns are reviewed.
Green links show where you are. © Copyright 2014 InspectApedia.com, All Rights Reserved.
Carson Dunlop's sketch (left) shows the proper locations for disposal of air conditioner or heat pump condensate.
[Click to enlarge any image]
Notice that one of the most common condensate disposal locations, connection to a plumbing stack vent pipe, is not recommended and is prohibited by building code in some jurisdictions.
Uniform Mechanical Code Section 310.0, 310.1 Condensate Disposal
Here is an excerpt from the Uniform Mechanical Code pertaining to the disposal of air conditioning condensate:
Condensate from air washers, air cooling coils, fuel-burning condensing appliances, the overflow from evaporative coolers and similar water supplied equipment or similar air conditioning equipment shall be collected and discharged to an approved plumbing fixture or disposal area.
If discharged into the drainage system equipment shall drain by means of an indirect waste pipe.
The waste pipe shall have a slope of not less than 1/8 inch per foot (10.5 mm/m) or one percent slope and shall be of approved corrosion-resistant material not smaller than the outlet size as required in either Section 310.3 or 310.4 below for air-cooling coils or condensing fuel-burning appliances, respectively.
Condensate or waste water shall not drain over a public way.
To clarify, an indirect waste pipe is something that is upstream of a trap. That means we cannot dump into anything downstream of a trap. That would include the main plumbing vent stack. -- [Thanks to Al Carson, Carson Dunlop Associates, Toronto]
ICC Model Building Code, Section 307: Condensate Disposal Regulations & Recommendations
The following HVACR condensate disposal recommendations summary cites, paraphrases, & comments on the widely adopted 2006 ICC model building code section on condensate disposal, section 307 
1. Requirement for a drainage system
For the two Types of Condensate: Fuel burning devices vs Evaporators & cooling coils
2. Types, sizes, slope of Condensate Drain Piping
4. Acceptable Condensate Drainage Terminations
5. Requirements for a Backup Condensate Drain System & Backup Condensate Drain Options
6. Other requirements for a condensate water-level monitoring device
7. Model building code requirements for a trap on the HVACR condensate drain system
Condensate Pan, Overflow Pan or Base Pan Cleaning Recommendations
We did not find cleaning requirements for condensate drip trays cited in the model building codes surveyed to date. However a read of manufacturer's installation instructions can provide further advice. For example:
Our photo (left) shows a white flexible tube used as condensate drain tubing for a split system air conditioning system being installed in a New York Home. (click photo to see an enlarged, detailed version). Photo courtesy Galow Homes.
Even now the drain is not perfectly sloped (note it's a bit high at that second cripple stud from left) but it was much worse before we re-routed the drain. The air conditioner installer had the drain line sloping up-hill in the area I've circled in the photo.
Having already had condensate drain line clogs and backups and leaks from the indoor air handler into the building wall at another split-system air conditioner where the condensate drain was improperly sloped and clog-prone, I was not going to let it happen again at this installation.
The installer thought I was being unreasonably demanding. But then, he was ignoring the plumbing code (1/8" per foot slope for condensate drain lines) and apparently didn't recognize the potential costs in rot, insect damage or mold if we simply let the condensate drain clog (due to an improper slope and dust that will enter the line) followed by leaks into the building wall up at the air handler.
See SPLIT SYSTEM AIR CONDITIONERS & HEAT PUMPS for complete information about the installation, routing, insulation, & protection of condensate drains for split system cooling or heat pump units.
CONDENSATE DRAINS - Air Conditioning or Heat Pump Condensate Drains Connected to a Building Plumbing Vent Pipe?
[Example air conditioning system inspection report language]: *** Safety Recommendation: this condensate line is connected to the house drain/vent piping - risking possible bacteria or even dangerous sewer gases entering the building air handling system.
Good practice (and some building and mechanical codes) includes a moisture trap (just as with other plumbing drains) and routing of the condensate to a wet drain line or preferably outside to discharge
into the gutter system or to the ground.
Sewer gases include methane which is an explosive gas. We don't want methane nor bacteria in our air conditioning system.
Here is a second example of improperly connected air conditioner condensate drain lines to a plumbing vent: the condensate line is connected to the house drain/vent piping; according to some experts and plumbing codes this is an improper plumbing connection, and for some lines there also is no condensate trap in this plumbing arrangement, risking possible bacteria or even dangerous sewer gases entering the building air handling system.
Good practice includes a moisture trap (just as with other plumbing drains) to help prevent this problem. Our understanding is that despite this very common installation found in our area, this is an improper plumbing connection which is dumping liquids into plumbing lines intended for dry-use only.
Correction by a qualified plumber does not usually involve significant expense.
Watch out: HEALTH NOTE: Condensate drains should not be connected directly to a house drain (without an air gap) as bacteria can grow back up the condensate line to contaminate building air, or sewer gases may be drawn up the drain and into the building air when the blower fan is operating.
Air conditioner condensate spillage in crawl spaces: is sometimes seen, especially if it's a dirt-floor crawl space.The installer probably figures the condensate will just "go away" through the soil exposed in the crawl area.
In our photo, the air handler itself was mounted in a crawl area, making service and repair more difficult and thus more costly. And spilling A/C condensate on the crawl space floor is asking for a building mold or insulation mold problem too.
Safety Hazards of Air Conditioning or Heat Pump System Condensate Leaks Onto a Furnace Heat Exchanger
Air conditioner condensate leaks into a furnace as we can see in these two photographs, can be dangerous. If the air conditioner condensate leaks cause rust holes in the furnace heat exchanger there is risk of dangerous flue gases, including carbon monoxide, leaking into the building air supply when the heater is running.
The rust seen in the bottom of the blower compartment tells us that this problem has gone on for some time. Further inspection of the heat exchanger is needed for damage, and on most systems, further inspection for mold contamination in the air handler and duct work may also be in order since the system has been spilling water into the air handler and perhaps the ductwork.
This photograph shows a typical point of disposal of air conditioning condensate outdoors, onto the ground. This A/C condensate line originated at the air handler in the building attic, though at some installations we could be looking at condensate from a condensate pump located
in the building basement.
This photograph shows what seems to us to be a sloppy installation of air conditioner condensate drainage.
The installer has sent the condensate drain line outdoors (fine) through the building eaves or soffit (OK) but left the condensate drain pipe terminated where it drips onto a lower roof, splashing up and staining building siding, possibly creating a wear spot on the roof shingles, and thus perhaps a roof leak before the rest of the shingles are ready for replacement.
Condensate drains routed to hidden locations: What about installers who route a condensate drain to some hidden location? The drains in this photo might be ok, or maybe not - it depends. If they disappear into an inaccessible or not readily visible location such as a crawl space the system is asking for trouble - such as a wet moldy crawl space.
If the drains appear outside
or at some other visible location we're in good shape. In this particular case, the air conditioning system for the computer center of
a large college was draining onto the floor of a utility room where condensate ran along drywall and then across to a floor drain.
The drywall gave us a little area of mold to clean up but luckily nothing of any consequence. We could see the ends of this drain
if we looked long enough.
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.
Green link shows where you are in this article series.
Frequently Asked Questions (FAQs)
No FAQs have been posted for this page. Try the search box below or CONTACT US by email if you cannot find the answer you need at InspectApedia.
Questions & answers or comments about air conditioner or heat pump condensate drain installation, leaks, clogs, troubleshooting, repairs
Check the FAQs just above, try the search box just below, or if you prefer, post a question or comment in the Comments box below and we will respond promptly.
Search the InspectApedia website
HTML Comment Box is loading comments...
Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.