I recently replaced the condensate drain line from my central AC evaporator, and I noticed that it emptied into a section of 1-1/4 in. PVC pipe embedded in the slab. I suspected that the pipe was connected to my sump, but when I ran a garden hose into the pipe for over five minutes, no water showed up at the sump. Could the pipe be connected some sort of dry well, and is it wise to drain any water through the slab?
Tom Kadesch, Gaithersburg, MD
Rex Cauldwell, a master plumber and electrician in Copper Hill, Virginia, replies: It is not a good practice to dump any water under a concrete slab. In sufficient quantities, water under a slab can cause subsidence, which may weaken the slab. Also, water can flow into your basement through the pipe as easily as it flows out. I recommend capping the pipe. (You might want to ask your local inspector why such a drain was approved.)
If the sump is within a reasonable distance, I’d run the condensate line directly into it. Never connect a condensate line directly to a drain line. Always run the line to a drain trap. Condensate pumps are available to pump water to a trap, such as a trap for a clothes washer. In some areas, code allows the condensate line from the pump to be run directly outside.