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Air Conditioning condensate pumps, and their proper installation InspectAPedia®  -     Air Conditioning condensate condensate pumps, and their proper installation Air Conditioning Condensate Handling Defects A/C condensate piping, leaks, hazards

This chapter of "How to Inspect the Central Air Conditioning or Cooling System" discusses the inspection of air conditioning condensate systems, including Air Conditioning 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. Contact us to suggest text changes and additions and, if you wish, to receive online listing and credit for that contribution.

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CONDENSATE PUMPS - Air Conditioning Condensate Pump Installation & Repair

Air conditioner condensate pumps are a convenient way to collect and dispose of the condensate produced by an air conditioning system when the air handler/cooling coil are located in a building location where the cooling condensate cannot be drained away by gravity. The most common situation is the need to dispose of air conditioner condensate produced by an air handler which is installed in a building basement or crawl space.

How an Air Conditioner Condensate Pump Works

Air conditioner condensate is water removed from the building air as that warm, moisture-containing air moves across the cooling coil in the building's air conditioning system's air handler or blower unit. The photograph shown here is of a common air conditioner condensate disposal pump. It's a little hard to see the pump's drain tube but it's that clear plastic tube in the upper left of this photo. If you are really alert you may have noticed those two capped-off copper tubes protruding from the concrete floor in the foreground of this photo. This pair of tubes is a convincing indication that there was an oil tank, probably a buried oil tank, installed at this property - a topic that needs further investigation. See Oil Tanks - The Oil Storage Tank Information Website, for details on that topic. Don't let our focus on any individual building concern make us miss another, possibly important discovery. The air conditioner condensate pump photo at the very top of this page shows an air conditioning condensate pump installed in an attic where it was used to move condensate across to a final condensate disposal point. The white piping is a gravity drain that moves condensate from the attic air conditioner air handler down into the condensate pump reservoir. We can't see much of the condensate reservoir beause the installer placed this pump down into the attic floor (so that she could drain condensate into it by gravity). The copper tube looping in the air is the drain line through which the condensate pump is moving condensate out of its reservoir to a disposal point. You can also see the black electrical wire bringing power to the condensate pump. The black round motor with a white label is the motor that powers the condensate pump. The black rectangular device is a voltage transformer that converts the building's 120V to the voltage needed by the pump motor. In the background of this interesting photograph we see a blue sump pump with a green garden hose connected to it. We surmise that the owner had previously tried to use this sump pump to remove condensate from the attic air handler. Stains suggest that the attic floor has previously been wet by air conditioner condensate spillage, perhaps leading to the more careful condensate pump installation shown here.

Sequence of Steps in the Operation of an Air Conditioner Condensate Pump

• Moisture laden warm air moves across the cooling coil in the air conditioner. As the air is cooled, moisture leaves the cooler air and condenses on the surface of the cooling coil.
• Moisture on the surface of the cooling coil drips into a collector tray inside the air conditioner's air handler or blower unit
• Moisture, or now we'll call it water or air conditioner condensate, flows out of the collector tray into a drain opening and downwards in a pipe or perhaps a flexible tube where the water is conducted to the entry opening of an air conditioning condensate pump unit.
• The air conditioner condensate pump includes a small water reservoir which receives the condensate from the air conditioner. As the water level rises inside this small reservoir a float switch located there is lifted by the rising water.
• When the water level inside the air conditioning condensate pump rises to a near-full level, the float switch turns on a small electric motor (the air conditioner condensate pump requires electricity to work and has to be plugged-in).
• The air conditioner condensate pump motor and pump move water out of the air conditioner condensate pump reservoir upwards in a drainage pipe or tube, usually flexible plastic tubing.
• The air conditioner condensate pump drain tube conducts the water produced by the system upwards to a building drain or in some conditions, outside, where it is disposed of as wastewater.

Proper and Improper Places to Route and Connect an Air Conditioner Condensate Pump Drain Line

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 - a common error in disposing of air conditioner condensate in attic installations. -- [Thanks to Al Carson, Carson Dunlop Associates, Toronto]

Acceptable methods to dispose of air conditioning condensate from a condensate pump

• Building drains with an air gap: The air conditioning condensate pump drain line should be routed to a building drain using an air gap such as that which is used by washing machines. Often we'll see the AC condensate drain line simply routed over to a washing machine drain in the basement.
• A building sump pump: often the air conditioning condensate pump drain line is routed across a basement to a basement sump pump system where the condensate wastewater joins other water which is collected and pumped out of the building by a larger sump pump.

Air conditioning condensate drain connections which are not recommended or are not best practice

• Air conditioner condensate spillage on basement floors is often found where an installer simply places the condensate pump drain line on the building floor where it ends near a floor drain. The nice feature of running condensate into a floor drain is that during the cooling season we're assuring that we keep the floor drain trap (let's hope there's a trap) primed with water, avoiding a sewer gas backup. Of course this means in dry weather or winter weather when the air conditioner is not running and the trap dries out, we may have a problem with radon or sewer gases entering through the dry floor trap. But a more common problem we find is that the plastic drain tube has been kicked aside and we see condensate running across the floor. In some buildings we've found that this wet condition has caused damage to building flooring, paneling, or drywall, leading to a mold contamination problem.
  
  
• Airtight drain connections Best practice will not connect an air conditioner condensate pump directly by an airtight piped connection to a sewer line without an air-gap. We don't want a possible sewage backup to send wastewater backwards down into the condensate pump and out of the pump's overflow opening onto the building floors. We understand the terms "indirect waste pipe" in the code citation above to refer to this condition and to the need for an air gap.
  
  
• Air conditioner condensate spillage on sidewalks is often found where the installer simply routed the condensate pump drain through a building wall to the outdoors in an urban area. We also see this condition almost without fail in urban and commercial settings where there is a transom-mounted air conditioner whose back-end simply drips onto the sidewalk below. Such installatins are inviolation of common plumbing codes such as that cited just above.

What else goes wrong with air conditioning condensate pumps

In our experience these little devices are pretty reliable and useful. But a few things do go wrong, some more often than others. Kinked or clogged condensate removal tubes can prevent the condensate pump from discharging its water successfully. When this happens air conditioning condensate will just spill out of the pump reservoir into the building. Watch out for kinks in the pump drain tubing, and watch out for low loops in the tubing that collect algae, dirt, or other muck that can clog the tube. Poorly-secured condensate pumps in a few locations have been found moved by occupants (kids) or tipped over or even stepped-on as you can see in the photo above. This unit was working fine, it just looked ugly. Burned up condensate pump motors have never been reported to us nor have we found one, but it's possible.

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• Thanks to Mark Cramer, Tampa Florida, for assistance in technical review of the "Critical Defects" section and for the photograph of the deteriorating gray Owens Corning flex duct in a hot attic. Mr. Cramer is a Florida home inspector and home inspection educator.
• 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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Books & Articles on Building & Environmental Inspection, Testing, Diagnosis, & Repair

• Our recommended books about building design, inspection, and repair, and about indoor environment testing, diagnosis, and cleanup are at the InspectAPedia Bookstore.
• Complete List of Air Conditioning & Heat Pump Design, Inspection, Repair Books at the InspectAPedia Bookstore.
• Modern Refrigeration and Air Conditioning, A. D. Althouse, C.H. Turnquist, A. Bracciano, Goodheart-Willcox Co., 1982
• 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
• 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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