Air Conditioning condensate drains, condensate pumps, and their proper installation InspectAPedia® -
Air Conditioning condensate drains, condensate pumps, and their proper installation
Air conditioning condensate drain leaks
Air conditioning condensate drain clogging - how to de-clog the A/C condensate line
Air Conditioning Condensate Handling Defects
A/C condensate piping, leaks, hazards
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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. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.
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 condenate. 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
Here is an excerpt from the Uniform Mechanical Code pertaining to the disposal of air conditioning condensate:
Section 310.0, 310.1 Condensate Disposal:
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]
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.
The condensate drain line and refrigerant tubing (black-insulated in the photo) were installed and the wall was prepared for blown-in insulation. Once the wall was insulated and drywall was installed, repairing an improperly-sloped drain line would have been much more costly and disruptive.
You'll see that we also installed nail plates to protect the condensate drain and refrigerant tubing from being punctured by screws or nails to be used when the drywall was installed.
Incidentally the same installer violated the manufacturer's recommendations against compressing the insulation on the refrigerant lines - one more picky issue that we decided to let go since the wall was to be insulated with blown-in foam.
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.
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.
HEALTH NOTE: Condensate drains should not be connected directly to a house drain 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.
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.
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.
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
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.
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.
Air Conditioning or Heat Pump Condensate Drains Routed to Hidden Locations
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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Additional technical contributors & reference sources for this article are listed below.
Use links just below or at the left of each page to navigate this document or to view other topics at this website. Green links show where you are in our document or website.
Carson Dunlop, Associates, 120 Carlton Street Suite 407, Toronto ON M5A 4K2Toronto. (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.
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.
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.
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.
The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop. The Home Reference Book 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. InspectAPedia.com ® author/editor Daniel Friedman is a contributing author. Field inspection worksheets are included at the back of the volume.
"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]
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.).
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