Came back out from previous estimate call. Inspected ductwork and MORE sand had filled the duct lines, each in slab duct line has a cube shaped junction box that is for that specific line. These boxes make the possibility of moving an inspection camera or hose past them impossible. The ductwork overall shows little to no signs of water or rust. Inspected supply plenum under the coil and it was filled to the top with sand. After going over options, customer would like to remove sand to see if we can find a source for the break and seal it. Spent 1 hour removing about 64 gallons of sand from plenum and removed enough to see the plenum for inspection. I was unable to see enough to find a break. Spoke to homeowner about options to flip ductwork or proceed with removing coil and furnace to find break and if possible seal it off. At this point quoted to remove furnace and coil, will come back Thursday 12/10/20 for an 8-10 call time. Left system so that it can run if needed, spoke to custom