Over the weekend, I got a call from a regular customer who manages a two-story building. Water was showing up inside a wall and had already started getting the floor and carpet wet. Before I started, I warned him that we were probably going to have to open the wall to find the source of the leak.

Once I opened it, we found the problem. An air-conditioning condensate drain had been connected to the building drain with a wye concealed inside the wall. The connection had come loose, so every time the unit produced condensate, some of that water was draining directly into the wall instead of into the drainage system.

There was another problem with the installation: condensate drainage has specific plumbing-code requirements. You can’t simply make a concealed direct connection to a sanitary drain because there happens to be one nearby. The condensate has to discharge through an approved method that protects the system from the sanitary drainage system and also allows the connection to be properly serviced.

We removed the improper connection from inside the wall and rerouted the condensate to the bathroom lavatory plumbing at an approved location above the P-trap. It’s a relatively small plumbing detail, but when it’s done incorrectly and hidden inside a wall, a small amount of condensate can eventually cause a considerable amount of water damage.