Sand in ducts is a pretty common problem we hear a lot about here at Trenchless Innovations. Most people tend to think their furnace filter traps it and keeps it from entering their ducts. Sadly, this is not always the case. Sand actually enters your air ducts due to the configuration of your system and the way air flows from it. 

Furnace Types Explained 

Furnaces are either upflow or downflow.  This article from our friends over at highlights the differences between the two. Slab homes with underground air ducts contain downflow furnaces. A downflow furnace blows air into a distribution box located in the floor, directs it to individual duct runs where it then flows to the floor registers. When your underground air ducts were installed, they were laid in a trench and bedded with sand beneath and around them before cement was poured over them.  

How Does Sand Enter My System?

Over time, your air ducts and distribution box will begin to rust. When this happens, small holes develop within them.  When you turn your furnace on, sand escapes through these small  holes and is drawn into your ducts. And because your filter is located on the intake side of your furnace, it is not able to catch any of the loose sand.  So if you’re experiencing sand floating throughout your home, it is actually the backfill sand that is surrounding your ducts and distribution box.

The below diagram illustrates a downflow furnace and what happens when your underground ducts begin to deteriorate. If you’re experiencing this problem or any other problem with your underground ducts, give Trenchless Innovations a call today! We’ll quickly get our team of experts out to your home to perform a camera inspection of your ducts and we’ll also provide you with our best recommendation on how to correct your duct problems! (708) 758-5070

Diagram showing downflow furnace configuration and how sand can enter ducts