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Air Conditioning condensate drains & pumps: installation codes & recommendations
- Air Conditioning condensate drains and their proper routing, installation, traps, slope, connections & installation
- Air conditioning condensate drain leaks, locations, causes, repairs
- Air conditioning condensate drain clogging - how to de-clog the A/C condensate line or drain pump
- Air Conditioning Condensate Handling defects lead to condensate spillage, leaks, mold
- Where should the air conditioner or heat pump condensate drain be connected - where are we permitted to dump condensate?
- Examples of Model Building Codes Condensate Disposal Regulations & Recommendations
- CONDENSATE HANDLING - home
- DRIP TRAY DEFECTS - separate article
- CONDENSATE LEAKS - separate article
- CONDENSATE PUMPS - separate article
- CONDENSATE DRAINS
- CONDENSATE DRAIN CLEAN & DE-CLOG - separate article
- CONDENSATE TRAY CLEANING - separate article
- Questions & Answers about air conditioner or heat pump condensate drain installation, leaks, clogs, troubleshooting, repairs
- References
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InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.
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. 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 links show where you are. © Copyright 2013 InspectAPedia.com, All Rights Reserved. Author Daniel Friedman.
What are the Proper Locations for A/C or Heat Pump Condensate Disposal
Carson Dunlop's sketch (left) shows the proper locations for disposal of air conditioner or heat pump condensate.
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.
Plumbing Code Citation for Installation of Air Conditioning Condensate Drain Piping
Carson Dunlop Associates sketches (left) illustrate both acceptable and not-recommended locations for the discharge of an air conditioner or heat pump condensate drain line discharge.
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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]
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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 [7]
1. Requirement for a drainage system
For the two Types of Condensate: Fuel burning devices vs Evaporators & cooling coils
- 307.1 requires that liquid condensation from fuel burning appliances be collected and discharged "to an approved plumbing fixture or disposal area in accordance with the manufacturer's instructions"
- 307.2 requires a condensate drain system for appliances containing evaporators or cooling coils, conducted from the appliance drain pan to an approved destination
2. Types, sizes, slope of Condensate Drain Piping
- 307.1 Condensate drain piping must be corrosion resistant for condensate from fuel burning appliances. using "corrosion-resistant material" and sized "no smaller than the drain connection on the appliance"
- 307.2.2 Condensate drain piping materials can be "... cast iron, galvanized
polybutylene, polyethylene, ABS, CPVC or PVC pipe or
tubing"
- Piping shall be at least 3/4" in diameter and ... shall not decrease in size ... [throughout its run from the condensate drain pan to its final disposal destination - no constructions by diameter]
- Horizontal runs of condensate drain piping slope at least 1/8" per foot in the direction of discharge. There is also a requirement for "uniform slope" and "uniform alignment"
4. Acceptable Condensate Drainage Terminations
- 307.2: "... Condensate shall not
discharge into a street, alley or other areas so as to cause a
nuisance." [i.e. do not discharge HVACR condensate over a sidewalk
5. Requirements for a Backup Condensate Drain System & Backup Condensate Drain Options
- 307.2.3 A secondary condensate drain system is required not in every installation instance, but in every installation at which "where damage to any building components will
occur as a result of overflow from the equipment drain pan
or stoppage in the condensate drain piping".
This backup condensate system requirement refers for example to an indoor air handler installed in an attic or in living space where leakage into the attic ceiling or onto a floor system could cause damage to the structure. Typical damage includes cosmetic leak stains, mold infections of wet drywall or insulation, structural damage from rot or inviting insect attack, and even, as one reader reports, unsafe collapse of a ceiling fan mounted below the leak area.
- 307.2.3 recommends any of the following methods for handling a backup condensate overflow protection system:
- 1. An auxiliary drain pan with separate drain: an auxiliary condensate drain pan at least 1.5" deep and at least 3" larger than the length & width of the appliance beneath which it is placed, using corrosion-resistant material of adequate thickness (0.7mm galvanized metal or 1.6mm non-metallic e.g. plastic) with a separate drain installed under the equipment and discharged to a conspicuous point that will alert building occupants to a blocked primary condensate drain
- 2. A separate or secondary condensate overflow drain line connected to the primary or OEM equipment's drain pan at a higher level than the main drain, and discharged as in 1. above.
- 3. An auxiliary drain pan without a separate drain line but instead provided with a water-level detection device (a switch that senses the presence of water in the drain pan) conforming to UL 508. The water or condensate detection switch in the drainless condensate overflow pan is wired to shut down the equipment.
- 4. A water detection device (UL 508) that will shut off the equipment in event of blockage of the primary condensate drain can be installed in any of several locations that in essence detect that the primary drain is backing up: in the primary condensate drain pan, in the primary condensate drain line, or in the condensate overflow drain line, positioned to detect and shut down the equipment before the primary drain pan would overflow.
- An exception to this condensate backup or overflow protection requirement is made for fuel-fired appliances that already include features that automatically shut down the device should the condensate drain become blocked. This feature is found, for example, on some condensing heating boilers or furnaces.
6. Other requirements for a condensate water-level monitoring device
- Section 307.2.3.1 requires use of a water-level monitoring device to provide condensate overflow protection on equipment where there is no secondary condensate drain and no ability to install an auxiliary condensate drain pan. Quoting "This device shall
shut off the equipment served in the event that the primary drain becomes restricted. Externally installed devices and devices installed in the drain line shall not be
permitted."
7. Model building code requirements for a trap on the HVACR condensate drain system
- Section 407.2.4, Traps, requires that "Condensate drains shall be trapped as
required by the equipment or appliance manufacturer." We interpret this provision to defer to the equipment manufacturer's installation instructions.
Watch out: in our OPINION and as we discuss in these articles, while a trap on a condensate drain line, usually provided quite close to the condensate collection pan itself, can reduce the chances of sewer gases backing up from a condensate drain that has been connected to the building DWV vent piping (not a procedure we recommend), a conventional P-trap in the condensate drain will not protect against all sewer gas backup possibilities. In particular, when an air conditioner is shut down for long periods of time (say during the heating season) it is common for the water condensate contents of the trap to dry out, thus losing protection against sewer gas leaks backing up through that 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:
"In some installations, dirt or other debris may be
blown into the unit from the outside and settle in
the base pan (the bottom of the unit).
In some areas of the United States, a “gel-like” or “slime-like” substance may be seen in the base pan. Check it periodically and clean, if necessary." General Electric Zoneline® instructions [8][9]
Examples of Improper Disposal of Air Conditioning or Heat Pump Condensate Disposal
Condensate Drain Leaks & Clogging: Improper Slope
 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?
Sewer Gas & Bacterial Hazards at Air Conditioners
[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.
See CLEANING & Legionella BACTERIA. |
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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.
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A/C or Heat Pump Spillage in Building Crawl Spaces
 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.
What s/he failed to consider is the risks of a legionnaire's infection or a mold problem caused by spillage of water into an indoor, and in this case confined and rarely-inspected space.
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. |
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Air conditioner condensate spillage down building walls: such as the condensate from this attic air handler can stain
the building walls and is simply ugly.
An expert HVAC technician might also have something to say about those rust stains themselves - we
may be looking at rust from inside the air handler, indicating that A/C condensate is spilling and leaking around inside the
unit - perhaps we're actually looking at a hidden mold problem in this building - more investigation would be appropriate.
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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.
Disposal of Air Conditioning or Heat Pump Condensate Outdoors
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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.
There's basically no issue with disposing of condensate at this location, though this particular photo shows two more subtle points to watch:
- There is some soil subsidence going on where the condensate is dripping, telling us that the soil around
the foundation is fresh, loose backfill. Watch out that the air conditioner compressor/condenser unit does not begin to tip as this backfill settles further from the soil subsidence that will accompany rainfall, snowmelt, and time. Concerns for tipping A/C condenser
units are discussed at Air Conditioner Compressor & Condenser Installation Errors.
- Foundation leaks: The second more subtle point to watch that has evidence in this photo is that little shrinkage crack we see
in the poured concrete foundation right where the A/C condensate is dripping. We might see water leaks into the building interior at this point if the foundation is visible indoors, or if the wall has been covered with finish materials we might have a mold problem.
I wouldn't go on to cut open such a wall to investigate this particular case further without other corroborating evidence. More about foundation crack diagnosis is available at How to Diagnose & Evaluate Vertical Foundation Cracks.
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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.
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Air Conditioning or Heat Pump Condensate Drains Routed to Hidden Locations
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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.
The discharge point of all of the air conditioning system
condensate drain lines, that is the system condensate drain and the air conditioner condensate overflow pan drain,
must be readily observable. (Ref. Uniform Mechanical Code
Sec. 1205 and Sec. 510. Condensate overflow pan is suggested for attic space per UMC (Uniform Mechanical Code) Section 1205.)
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.
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Technical Reviewers & References
Related Topics, found near the top of this page suggest articles closely related to this one.
Click to Show or Hide Citations & References
 Carson, Dunlop & Associates Ltd., 120 Carlton Street Suite 407, Toronto ON M5A 4K2. (416) 964-9415 1-800-268-7070 info@carsondunlop.com. The firm provides professional home inspection services & home inspection education & publications. Alan Carson is a past president of ASHI, the American Society of Home Inspectors. Thanks to Alan Carson and Bob Dunlop, for permission for InspectAPedia to use text excerpts from The Home Reference Book & illustrations from The Illustrated Home. Carson Dunlop Associates' home inspection education products include
- The ASHI-adopted Home Inspection Training Program, and Commercial Building Inspection Courses
- The Home Inspection Home Study Course, and publications such as
- The Home Reference Book, a reference & inspection report product for building owners & inspectors.
Special Offer: Carson Dunlop Associates offers InspectAPedia readers in the U.S.A. a ten percent discount on any number of copies of the Home Reference Book purchased as a single order. Just enter HRBUS10 in the order payment page "Promo/Redemption" space.
Note: InspectAPedia.com ® editor Daniel Friedman is a contributing author.
- The Home Reference eBook, an electronic version for PCs, the iPad, iPhone, & Android smart phones
- Home Inspection Report writing materials, including the Horizon Software System that manages business operations, scheduling, & inspection report writing using Carson Dunlop's knowledge base & color images. The Horizon system runs on always-available cloud-based software for office computers, laptops, tablets, iPad, Android, & other smartphones.
- The Illustrated Home illustrates construction details and building components, a reference for owners & inspectors
- Eric Galow, Galow Homes, Lagrangeville, NY. Mr. Galow can be reached by email: ericgalow@gmail.com or by telephone: 914-474-6613. Mr. Galow specializes in residential construction including both new homes and repairs, renovations, and additions.
- [3] Reader Stuart Oakner suggested the Mighty Pump (below) as a method for clearing clogged or blocked air conditioning or heat pump condensate drains.
- [4] Mighty Pump, is a manual pump that is used to clean or clear out a debris-clogged A/C or heat pump condensate drain. The kit from acdrainpump.com includes a reversible, hand operated pump and flexible inlet and outlet hoses designed along with an adapter to connect the pump to a 3/4" condensate drain line. The company can also be contacted by email to Info@ACDrainPump.com.
- [5] Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
- [6] Simpson Strong-Tie, "Code Compliant Repair and Protection Guide for the Installation of Utilities in Wood Frame Construction", web search 5/21/12, original source strongtie.com/ftp/fliers/F-REPRPROTECT09.pdf, [copy on file as /Structures/Framing/Simpson_Framing_Protectors.pdf ]. "The information in this guide is a summary of requirements
from the 2003, 2006 and 2009 International Residential Code
(IRC), International Building Code (IBC), International Plumbing
Code (IPC), International Mechanical Code (IMC), 2006 Uniform
Plumbing Code (UPC) and the 2005 National Electrical Code." broad. Puerto Rico and the U.S. Virgin Islands enforce one or more of the I-Codes.
- [7] 2006 ICC Model Building Code Chapter 3, General Regulations, New Jersey Mechanical Code, web search 8/2/2012, original source: http://www2.iccsafe.org/states/newjersey/NJ_Mechanical/PDFs/2006_Chapter%203-General%20Regulations.pdf
Quoting about the ICC:
The International Code Council (ICC) was established in 1994 as a non-profit organization dedicated to developing a single set of comprehensive and coordinated national model construction codes.
The International Code Council is a member-focused association dedicated to helping the building safety community and construction industry provide safe, sustainable and affordable construction through the development of codes and standards used in the design, build and compliance process. Most U.S. communities and many global markets choose the International Codes.
The International Codes, or I-Codes, published by ICC, provide minimum safeguards for people at home, at school and in the workplace. The I-Codes are a complete set of comprehensive, coordinated building safety and fire prevention codes. Building codes benefit public safety and support the industry’s need for one set of codes without regional limitations.
Fifty states and the District of Columbia have adopted the I-Codes at the state or jurisdictional level. Federal agencies including the Architect of the Capitol, General Services Administration, National Park Service, Department of State, U.S. Forest Service and the Veterans Administration also enforce the I-Codes. The Department of Defense references the International Building Code for constructing military facilities, including those that house U.S. troops, domestically and a ...
- [8] "GE Zoneline® Owners Manual and Installation Instructions, Heat/Cool Model 2900, Heat Pump Model 3900", General Electric Corporation, [copy on file].
- [9] "GE Zoneline® Owners Manual and Installation Instructions, Heat Pump Model 5800", General Electric Corporation, [copy on file].
- [10] "Whirlpool WGPH45 Packaged Heat Pump, Product Specifications", Whirlpool Corporation, [copy on file].
- 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
 Air Conditioning SEER - New DOE Air Conditioner and Heat Pump Efficiency Standard-
Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair
 The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 25th Ed., 2012, is a bound volume of more than 450 illustrated pages that assist home inspectors and home owners in the inspection and detection of problems on buildings. The text is intended as a reference guide to help building owners operate and maintain their home effectively. Field inspection worksheets are included at the back of the volume. Special Offer: For a 10% discount on any number of copies of the Home Reference Book purchased as a single order. Enter INSPECTAHRB in the order payment page "Promo/Redemption" space. InspectAPedia.com editor Daniel Friedman is a contributing author.
Or choose the The Home Reference eBook for PCs, Macs, Kindle, iPad, iPhone, or Android Smart Phones. Special Offer: For a 5% discount on any number of copies of the Home Reference eBook purchased as a single order. Enter INSPECTAEHRB in the order payment page "Promo/Redemption" space.
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