On a recent home inspection in Montgomery, water was found in the HVAC duct that serves multiple lower level rooms. This duct system was installed in the concrete slab.
Water here indicates that the duct has been compromised, allowing ground water to enter. This can lead to many other problems, such as poor indoor air quality, radon entry, elevated moisture levels in the house, and so on. Unfortunately, there is not an easy solution to this problem. However, there are companies that can reline the ducts, or installed new ducts in the ceilings of the lower levels. In either case, be prepared because repairs will be costly.