Built and installed full length return plenum. Attached existing 16 inch return duct to the new plenum. Installed new 16x24 return filter grill in the hallway. Built and installed return plenum for the new return cut in. Ran new 14 inch return duct to the system. Sealed all ductwork connections with mastic and hardcast. Cleared primary drain with CO2 and primed trap with water. Tested operation of system. Everything is working at completion of install.