AC Drain Line in attic

Thank you! Problem solved. I poured a cup of bleach down the line and then shopvac at the other end and got about half a gallon out. I appreciate the advice.

What line did you attach vac to? If you are leaking water from the drain pan line, that means your main line is clogged. I am asking because the clog is in your main drain line which usually empties into a sewer drain line, like a bathroom sink line, etc. Just pointing this out for you to be aware that if the pan fills up again, your main drain line is still clogged.

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I can't pinpoint where and how the water is getting around the pan, so I am fearing this plastic pan is cracked somewhere.

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If you are absolutely sure the primary condensate drain is not clogged that does suggest the primary drain pan could be cracked.

You sure you might not have a partial clog in the primary drain line that allows some drain water through, but not all, causing the primary drain pan to overflow into the secondary (emergency) drain pan during long run times? The amount of condensate water produced in an hour run time can be as high as a couple gallons.

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I've lived in houses where they drain outside.

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Thanks for pointing that out. I was mentioning it just in case what I described may be his situation.

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I am asking because the clog is in your main drain line which usually empties into a sewer drain line, like a bathroom sink line, etc. Just pointing this out for you to be aware that if the pan fills up again, your main drain line is still clogged.

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This was my situation, and I had to disconnect where it went into my wall so I could hook up the vac and clear the line. Then went back and installed a Tee before reconnecting for future issues

In this case, the main drain line leaves the unit, travels across the attic, and then goes down through the wall to the basement ceiling, where it travels another 25 feet to the outside wall.

I have previously extended this exit point with a garden hose to pull it away from the foundation. That is where I attached the vacuum.

I've got a french drain on mine because I had this problem so frequently with the drain line being clogged going into the main home drain line.

It's been great so far.

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When you change filters monthly, pour some white vinegar in the drain line. It will keep it clear.

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Was coming to post about vinegar. Don’t use bleach.

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When I take the side cover off the blower, the plastic drain pan is nearly dry. And I can pour water freely down the normal drain.

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Do you have an air handler unit (AHU), often referred to as Fan Coil, or a gas furnace?

The difference, as it relates to the condensate drain, is the evaporator coil in a AHU is upstream of the blower motor, and under negative air pressure when the AC is operating and thus requires a u-trap or p-trap in the condensate drain, with a vent downstream of the trap, for it to drain properly. The air vent downstream of the water trap allows the water to drain if there is an another water trap (usually a bow in drain pipe). If the drain doesn’t have a properly designed water trap and a vent, the condensate water would not drain properly when the AC is running causing water to overflow into the secondary-emergency pan. If you are pouring water into the primary drain pan to test it with the cover off and the unit not running it’s going to drain properly b/c the system is not under negative air pressure.

In contrast, with a gas furnace the evaporator coil is downstream of the blower motor, under positive air pressure when running, and therefore doesn’t require a water trap to drain properly.

TLDR: if you have a AHU, check for proper design and installlation of a water trap and vent in the primary condensate water drain line, and kinks or bows in condensate drain line downstream of the water trap.

These short videos will explain with demonstrations.

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