we just had a new AC system installed in my florida house. the unit is in the garage, and the air handler is vertical with the evaporator on top.

the unit he removed had 2 condensate lines: one that drips outside on to the lawn and a second on that points at the floor but never dripped.

the new unit is only connected to the outside drain.

should the new unit have 2 drain lines?

1 Answer 1


No, probably not. The reason there are two lines is in case one gets clogged up, the second one will be used as a backup.

The reason for the backup line is if the unit is in the house, you absolutely don't want a clog in one drain line to cause water to drip out of the unit and get all over your house. Since it is in the garage though, it probably just doesn't matter much if you get water on the garage floor. Which is probably why the installer didn't bother installing a backup line (which it sounds like just drained onto the floor anyways)

  • should i be worried about the condensate backing up and dripping through the air handler/furnace and down in to the duct work?
    – longneck
    Commented Jul 26, 2010 at 20:05
  • @longneck - Personally, I wouldn't worry about it one bit. Commented Jul 26, 2010 at 20:12
  • The backup line is only a concern if the main one gets plugged up. You said it leads outside. Is there any way for crud to get into the outside line? If not, there is little chance of it getting plugged up (the condensate water is really clean). Commented Jul 26, 2010 at 21:10
  • Also, if it did plug up, how long before you would notice? Less than a day? A few drips on a concrete floor are pretty harmless. If it takes weeks for you to notice, then it's a bigger concern. Commented Jul 26, 2010 at 21:12

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