Tuesday, April 21, 2009

Water in duct work under slabs and crawlspaces

From time to time, we receive calls about homeowners hearing gurgling noises coming from their ductwork. Sometimes they see the water in the duct under their registers, or their ducts completely stop working because they are completely under water. Water flooding the ductwork is most likely to occur in slab foundations, but I have seen it happen in crawlspaces as well.

In the 50s and 60s, some builders used clay tiles as ductwork in or under the slabs. As the soil settled, expanded, and contracted, the ductwork would crush or crack. Most of the seams were not sealed, so sand and silt would clog them; or moisture would enter the duct. From the 40s to the early 80s, many builders used metal ducts. Over time, most metal ductwork under the slab will rust allowing moisture, silt, and mud to enter and clog the pipe. Thousands of homes have duct work in their slabs. In many low level areas with high water tables, water and moisture will infiltrate the ducts. Poor grading and downspouts overflowing would also allow water to enter the ducts. These home can suffer from major moisture problems.

With all of this moisture and dirt infiltration, bacteria and spores become a concern. The biggest issue is that these biogrowths and spores are funneled into the living area, and you end up breathing this poor indoor air quality. These contaminants are after the filter so there is nothing protecting you from them. Some of the pipes used in the cement under the slab had asbestos wrapping. If you are suffering from poor indoor air quality check out Jason Yost at www.SolutionsIEC.com

If you are suffering from water entering your ductwork in a slab or crawlspace foundation, give us a call @ 1-877-409-2837 or sign up for a free estimate at www.americanbasementsolutions.com.

Thanks for reading the rambling thoughts of a slab foundation inspector,

Larry Ralph Jr.



  1. So true! There are a number of pollutants that can become an issue in situations like this. Even in situations where the HVAC system is in sound condition, the effects of a moist and polluted environment, like that you describe in your article, can be felt through out a structure as these contaminants stack upward into the building materials and air. I've tested carpet, for example, that was cluttered with contaminants that had stacked up with the moisture from the crawl space. Anyone reading this article should consider installing a system that will aid in preventing these problems before they begin. Waiting can increase the cost of fixing a problem while installing your system (in some cases doubling the needed investment).

  2. What is the solution to fixing the leaking ducts under the concrete?


Please do not post your website as a link if you are not going to link back to ours from your website.