This article discusses the inspection and repair or un-clogging of condensate disposal systems, including air conditioning, heat pump or condensing boiler/furnace 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.
We discuss air conditioning, heat pump & condensing boiler or furnace 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
health and safety concerns are reviewed.
We also provide a MASTER INDEX to this topic, or you can try the page top or bottom SEARCH BOX as a quick way to find information you need.
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.
[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.
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
Note: new in 2015 is the ICC IMC 307.2.5 & IRC M1411.3.3 Drain Line Maintenance code for 2015
The ICC, under "Drain Line Maintenance" requires that
Condensate darins shall be configured to permit the clearing of blockages and performance of maintenance without having to cut the line. - ICC IMC 307.2.5 & IRC M1411.3.3 Drain Line Maintenance code for 2015, original source: http://www.iccsafe.org/
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
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
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
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 Drain Insulation Code?
Reader Question: 7 Feb 2015 Diane S said:
In SC, does the condensation line of an attic HVAC unit need to be insulated?
Diane, If your condensate line is not leaking but you are seeing condensation on its exterior such that the exterior moisture is enough to cause damage, then by all means, I'd insulate the line. It's not something I've come across nor have I seen it necessary. Model codes that I reviewed don't require that line to be insulated.
See ANSI/ASHRAE/IES Standard 90.1-2010 & 2012 IECC, "Insulation Requirements in Commercial Buildings for Mechanical and Service Hot-Water Piping"
ASHRAE Standard 90.1-2010, Section 184.108.40.206 HVAC System Pipe Insulation, lists HVAC piping requirements and as an EXCEPTION, excludes from that requirement "Piping that conveys fluids that have not been heated or cooled through the use of fossil fuels or electricity (such as roof and condensate drains, domestic cold water supply, and natural gas piping)" - retrieved 2/9/2015 original source www.energycodes.gov
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 
Improper Disposal of Air Conditioning or Heat Pump Condensate Disposal
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 Reader Stuart Oakner suggested the Mighty Pump (below) as a method for clearing clogged or blocked air conditioning or heat pump condensate drains.
 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.
 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.
 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 ...
 "GE Zoneline® Owners Manual and Installation Instructions, Heat/Cool Model 2900, Heat Pump Model 3900", General Electric Corporation, [copy on file].
 "GE Zoneline® Owners Manual and Installation Instructions, Heat Pump Model 5800", General Electric Corporation, [copy on file].
"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]
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