A/C Drain into sink vent?

Have an odd problem I temporarily solved with a hacksaw this week.
Several weeks ago, my wife called mid-afternoon from our house (in Houston) and water was dripping from a downstairs A/C vent and quite a bit. I rushed home from work and swapped out the bowls with a 5-gal bucket and went upstairs and the upstairs master bath was in worse shape. Water was dripping down the wall behind the sink.
Water was cool & clean and slowed when the A/C turned off. So, the A/C folks I called said to run vinegar through the drain line to clean out and they'd see how soon they could come up. I did this and traced the drain line in the attic as far as I could go with it, but couldn't see where it connected to our drain system, but it headed towards our master bath sinks.
I couldn't see anything unusual under the sinks and the sinks haven't plugged in awhile so not sure how this was an issue, but just for fun I climbed on the roof and snaked the vent I suspected was causing the trouble and sure enough I started smelling vinegar on the debris. This fixed it for a few weeks, then while on vacation it started up again (naturally) so this time I cut the drain line and am letting it fall into the pan under the A/C unit and drip from the emergency drain at the eave.
So, I suspect the A/C installer or plumber did a lousy job of sealing this all up or they should have routed the drain into a trap instead.
FYI, with the A/C running, I could fill up a 5-gal bucket overnight from the dripping we get.
So, any suggestions on the following courses of action?
1. Reroute the drain line to another sink vent that sees much less use (hair, etc..) 2. Route the drain to the eave and down the side of the house 3. Route the drain to an actual sink drain, not an air vent. 4. Call a plumber
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Have an odd problem I temporarily solved with a hacksaw this week.
Several weeks ago, my wife called mid-afternoon from our house (in Houston) and water was dripping from a downstairs A/C vent and quite a bit. I rushed home from work and swapped out the bowls with a 5-gal bucket and went upstairs and the upstairs master bath was in worse shape. Water was dripping down the wall behind the sink.
Water was cool & clean and slowed when the A/C turned off. So, the A/C folks I called said to run vinegar through the drain line to clean out and they'd see how soon they could come up. I did this and traced the drain line in the attic as far as I could go with it, but couldn't see where it connected to our drain system, but it headed towards our master bath sinks.
I couldn't see anything unusual under the sinks and the sinks haven't plugged in awhile so not sure how this was an issue, but just for fun I climbed on the roof and snaked the vent I suspected was causing the trouble and sure enough I started smelling vinegar on the debris. This fixed it for a few weeks, then while on vacation it started up again (naturally) so this time I cut the drain line and am letting it fall into the pan under the A/C unit and drip from the emergency drain at the eave.
So, I suspect the A/C installer or plumber did a lousy job of sealing this all up or they should have routed the drain into a trap instead.
FYI, with the A/C running, I could fill up a 5-gal bucket overnight from the dripping we get.
So, any suggestions on the following courses of action?
1. Reroute the drain line to another sink vent that sees much less use (hair, etc..) 2. Route the drain to the eave and down the side of the house 3. Route the drain to an actual sink drain, not an air vent. 4. Call a plumber
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bwalters wrote:

The condensate should never have been discharged into the sanitary vent. But, I guess it was easy for the installer. Be sure to plug whatever opening he made so sewer gas sin't escaping.
I think your best bet may the outdoor drain line you proposed. Think about what you'll do with the water once outside though. Some places may have restrictions on discharging to the ground.
You *can* discharge into an existing drain (in most places) where the drain is protected by a trap. It's often done with a branch on a sink drain (before the trap inlet). The sink useage keeps the trap filled and helps keep the drain flushed.
Jim
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