Restricted AC Condensate Drain Lines

The way your air conditioner dries your house is by removing moisture from the home. That moisture must go some where. The moisture is removed by condensing it on the cold refrigeration coils and letting it run to the exterior thru a condensate drain line.


As an Inspector I see a lot of  homes with water leaking from the upper AC condensate drain line.. This is a very common problem on homes that are 5-10 plus years old.
On a vacant home, where the AC unit has not been run,  this can be identified by observing rust stains on the upper drain line, and often on the exterior wall.  In the attic there will be excessive rust or standing water in the drain pan under the air handler.

Homes that have the AC unit /air handler in the attic have two condensate drain lines extended to the exterior. The upper line is commonly installed on the upper side of the home and often above a window.
     The lower line [primary line] will be installed apx. 2-3 ft. off the ground, usually on one of the ends on the home.  If you home has two or more AC units there will be two drain lines for every unit.

The role of your AC drain lines
. Primary Drain Line. This line is connected to the unit in the attic.
In the humid part of the summer several gallons of water will drain through this line every day.. To help prevent standing water, and a breeding ground for termites and bugs at your foundation,  installing a splash block to drain water away from the foundation is often recommended.
     A splash block, [a piece of tapered plastic apx. 8"wide and 12-16" long]  can be purchased at your local hardware store or at one the the big box buildiing supply stores. 

Upper Line. The upper drain line [ I consider this line a back up line]  is connected to a drain pan installed under your AC unit/air hander. This line is only used if the lower / primary drain line becomes plugged or restricted.  When this back up drain  line plugs up,  all of the water will drain in the home and cause water damage to the insulation, wood framing and ceilings.

Good rule of thumb.... Check your drain lines every couple weeks in the summer, if the water is leaking from the upper drain line, or if you don't see water leaking from the lower or upper lines,  call an AZ  Lic. AC contractor to service your unit and clean the drain  lines.
          *** Correcting restricted drain lines is not very costly if corrected as soon as you see it.
.             ***   Correcting water damage and possible mold damage can be very expensive.