Air Conditioning Condensate Drip Trays, Defects, Repairs
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• Air Conditioning Condensate Drip Trays, Defects, Repairs
• Air Conditioning Condensate Handling Defects
• A/C condensate piping, leaks, hazards
• Questions & answers about air conditioner and heat pump condensate drip trays, overflow pans, and safety switches, controls, and drains

A missing air conditioning system condensate drip tray risks leaks into the attic ceiling, where air conditioner condensate can damage the building or cause a (hidden) mold problem, especially if condensate is leaking onto the upper, hidden (by insulation) attic side of drywall forming a ceiling of a room located below the equipment. Both the drywall and the insulation itself may become mold reservoirs.

When an air conditioning unit is located in an attic where damage may result from air conditioning system condensate overflow from the primary condensate collection and drain equipment, an additional water-tight corrosion-resistant pan (an air conditioner condensate drip tray or "drip pan") should be installed below the air conditioning equipment to catch overflowing AC condensate should the primary AC condensate drain become clogged.

An alternative design provides one air conditioner drip pan with a standing overflow and a secondary air conditioner condensate drain. (Also, a basement air conditioning system condensate pump can overflow and spill into the living area if the condensate pump fails or if the condensate pump drain line becomes kinked or clogged.)

Air conditioning drip pan drains: The air conditioner's condensate overflow pan or tray requires its own separate drain. In the left photo above, the overflow pan has its own drain line, but it joins with the main air conditioner condensate drain line almost immediately.

A blockage in the condensate drain is going to lead leaks out of the air handler into the overflow pan. but since the overflow pan itself shares the same drain the pan will overflow into the building ceiling, inviting a mold problem or other damage.

But this is the most common way we see these drains installed. Most likely the installer is considering that the main risk of a blockage in the condensate drain system is going to be inside the air handler unit itself. We're not sure what data supports this view. The float switch approach, discussed next, might be a safer approach.

Float switches on condensate trays: Some air conditioning system air handler installations provide a float switch in the condensate overflow tray. This switch has a floating lever resting in the overflow pan.

The lever senses the presence of water and "floats up" until it shuts down the air conditioning system. This may be inconvenient in hot weather, but the installer or owner have chosen to protect the building against a potentially costly mold or other leak-related problem by shutting down the air conditioner, forcing attention to the problem.

Remember that if the condensate float tray switch senses condensate in the tray (or is otherwise defective) it will shut the air conditioning system down - if your air conditioning system seems ok but won't turn on, this switch could be one of the items to check. Thanks to Lester Richter for this tip.

Watch out: if your air conditioner has suddenly shut off and won't start, don't forget to check the condensate overflow tray for water, and if this switch was used (instead of a second condensate drain pipe), see if the switch is keeping your air conditioner turned off. If your condensate tray switch is a lever type (shown in our photo) try pushing the lever down to see if the A/C will turn back on. Other switches may have no moving parts: you'll need to remove the condensate and dry the switch.

An air conditioner condensate pan or drip tray float switch installed, the cost will principally be the fee for an HVAC service call to install the switch in the pan (trivial) and wire it to the A/C controls (less than an hour). Figure $100. to $150 for a service call to install the switch if none is already present. If there is an drain pan overflow shutoff switch already installed but needing replacement, it should be a simpler operation since it's just a swap-in part. The wiring to the HVAC system controls will already be in place.

The condensate pan or overflow pan safety switch itself, such as the Safe-T-Switch Model SS3 made by Rectorseal and sold as a drip pan overflow shut-off switch, retails from $30.00 to $50.00 U.S. [1]

Don't forget to find and fix the cause of condensate leakage into the overflow tray or you'll continue to have air conditioner operating problems.

See the other condensate handling diagnosis and repair articles listed here:

CONDENSATE HANDLING
  DRIP TRAY DEFECTS
  CONDENSATE LEAKS
  CONDENSATE PUMPS
  CONDENSATE DRAINS
    Locations for Condensate Disposal
    Plumbing Code for Condensate Drains
    Improper Condensate Disposal
    Condensate Drains Connected to Vent Pipe
    Condensate Spills in Crawl Spaces
    Condensate Leaks Onto Heat Exchangers
    Condensate Disposal Outdoors
    Condensate Drains to Hidden Location
  CONDENSATE DRAIN CLEAN & DE-CLOG
  CONDENSATE TRAY CLEANING

In this photograph of the interior of an air conditioner overflow drip pan or tray, the air conditioning system condensate overflow tray shows evidence of leaks.

Since normally condensate produced in the indoor air handler is carried from the air handler interior to a condensate drain, we don't expect to see condensate falling into the condensate overflow drip tray as a normal event.

If we see evidence of leaks into the condensate tray, the air conditioning system service technician should investigate the cause of this condition.

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.

• The Home Reference Book - the Encyclopedia of Homes, Carson Dunlop & Associates, Toronto, Ontario, 2010, $69.00 U.S., is available from Carson Dunlop, and from the InspectAPedia bookstore. The 2010 edition of 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.