Photograph of  improper condensate drain connected to plumbing vent line Condensate drains & pumps
Codes & recommendations for HVAC Condensate Drainage

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A/C condensate drains & pumps: codes, installation, leaks, clogs, connections, troubleshooting & repair:

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

Condensate leak 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

Condensate disposal locations (C) Carson Dunlop Associates

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.

Article Series Contents

Plumbing Code Citation for Installation of Air Conditioning Condensate Drain Piping

More AC condensate drain connections and destinations (C) Carson Dunlop AssociatesCarson 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.

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

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:

Devices or methods for providing condensate drain cleaning or de-clogging are discussed in this companion article: CONDENSATE DRAIN CLEAN & DE-CLOG

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

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

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.

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]

Improper Disposal of Air Conditioning or Heat Pump Condensate Disposal

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HVAC Condensate Articles

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