I bought a new 5k iMac and need to take my old iMac [Late 2013] in for the HD replacement recall. I cannot find a way to wipe out my 3TB fusion drive as I was able to with old version of Disk Utility. I was able to wipe the HD and then use Recovery to reinstall the OS last time I sold my last iMac. Also, I have to enter my username and password when reinstalling El Capitan. My main concern is wiping the 3TB hard drive, I would feel better making sure the contents of the drive are ANNIHILATED first. I assume Apple will destroy the drive and then send back to Seagate for credit but would prefer the aforementioned safeguard just in case.