We came out to televise some underground duct work for a customer to find the lines were filled with water and mud/dirt. We recommended running the downspouts out away from the house to lower the water table from rising up under the slab allowing water to enter the ducts. Sure enough a few weeks later the water was gone, then we were able to clean all the duct work, also spin cast mortar the bad metal pipes/ connections for structure. Finally we applied duct armor to seal the HVAC system.