try this sugestion by another member from a different forum. many users tried this and said it worked
HevvyDSep 29, 2016 8:56 PM(
in response to luniacdevel)
Here is a quick understanding of the situation:
When a file gets deleted without any Time Machine backup, MacOS has a feature of a local Time Machine backup, which saves the file into the System section as shown in the About This Mac> Storage. The purgeable space is saved for whenever a local time machine backup needs to occur if in case any file had been deleted accidently from the system by the user. There is a way to disable this local time machine backup. Here are the following steps:
1. Open terminal
2. Type "df -h". This will show you a volume of MobileBackups if it was enabled and if this does apply to your system.
3. To disable your Mobile Backup, type "sudo tmutil disablelocal". When prompted for password then type in your password.
4. Check your Storage and see that the purgeable space has been deleted plus the System section has also shrunk to just contain the OSX.
To enable/re-enable the local Time machine backup:
1. Open Terminal
2. Type "sudo tmutil enablelocal". When prompted for password then type in your password. This will then start making a local time machine backup in the system. This will take a while. If you want a quick backup then type "tmutil snapshot".
3. Check your Storage to see that the backup has been made with minimal amount of purgeable space since the snapshot was made. Note that the system section has also increased at this point too to include the previous backup but this time without the space for the purgeable space reserved for this size.