We are installing a sump pit and pump out side of the slab home and installing a section of drain tile under slab lower than the duct work connecting into new sump pit and pump discharging pump away from house to relieve ground water to prevent water from entering underground duct work.
Televised ducts under slab floor. Ducts are concrete with metal connections and fittings. Plenum is rusted and has a pump installed in it. Suggest installing an outside sump pit and pump to lower water level then spray lining ducts with Duct Armor duct lining material.