A/C Condensate lines – primary & secondary

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Published: April 22, 2014 Last Updated: January 29, 2021

Condensate is the water that comes from your A/C evaporator coils when the system is running. It is normal to have condensate. This condensate water generally goes into a pan that is under the system or is built into the unit. From there, the condensate water is usually disposed of by several different methods, depending on the age and type of system.

Condensate dripping from a condensate line is normal. However, if it is dripping out of a secondary line, then it generally means the primary line is clogged. When the primary line is clogged, an HVAC contractor is normally called and will unclog the line. This is considered a relatively quick and easy task and some homeowners will do it themselves.

Primary and secondary lines


Many units that are located in attics or similar places will have two condensate lines. One is the primary condensate line that is generally connected to a location, like a tail piece of a bathroom sink drain piece.


The secondary line is considered a backup line, so that if the primary line gets clogged, the condensate water will then go through the secondary line. The secondary line (usually a PVC pipe) will often end in a highly visible and conspicuous location.


  • Above an exterior door
  • Above an exterior window
  • Above a bath tub ( a PVC pipe sticking out of the ceiling above the tub)


Remember, if water is dripping from the secondary line, then the primary line is probably clogged and needs to be unclogged.

A word of caution

Take a few minutes and check for stains near the HVAC unit or along the path or the condensate line. Look for moisture or mold and mildew like stains or discolorations; because where there’s moisture over a long period of time, there may be mold and mildew. If the unit is in the attic check around the unit, the platform that the unit is on and insulation near the unit. Also, check for stains on the drywall ceilings under the unit.

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I am having a issue with my ac primary and secondary line . I feel I am being ripped off ,the primary has had a plug since 6/2016 .i recently attached a section of pvc to the primary,because the secondary was removing the condense water,do I have to creat positive pressure so the the water will exit out the primary?

I have seen on a new structure, a secondary condensate line from an attic drain pan. It terminates to a tail piece through the attic floor and sheet rock of a finished garage 14 feet above the floor! Does not seem right to me!

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