Why does my Galaxy Tab A 10.1 internal storage keep filling up?

[Android Central Question]

I have 16 gb internal storage with 3.1 gb installed apps the other apps are pre-installed and other than the MS office apps would delete most if I could I have 46 mb of data on the internal drive - all my music and photos are in the cloud or on sd card.
The tablet keeps filling up -the entire internal storage. This causes apps to crash. I cannot even keep a word document open in OneDrive. I need this for work - this damn thing is useless- a $300 paperweight!
Samsung disabled the android feature that allows one to format SD card as internal storage.
I go in weekly and uninstall updates and apps and have turned off auto updates for all but vital apps-I clear the caches regularly. Last week I uninstalled 2gb worth of apps and had 2 free gbs -today the tablet is completely full again. Samsung tech support is useless and know nothing.
WHAT IS CONSTANTLY FILLING UP MY INTERNAL STORAGE??? Is there anything I can do to stop it short of rooting? Any help greatly appreciated

 

[B. Diddy]

Welcome to Android Central! Try DiskUsage to get a better idea of what's taking up that space.

 

[Rukbat]

For an even better idea (you need to know how much internal storage you have - it's not 16GB), install and run Terminal Emulator for Android. Enter the command

df

and tap the enter key.

The last line should end in userdata, emulated/0 or sdcard (sdcard is internal storage - external storage is extSdCard). The numbers on that line will tell you how much internal storage is available to you - the rest is used by Android.

To keep from filling the tab up, use an SD card to hold your docs, pictures, spreadsheets, etc. It should be able to handle up to a 512GB card at the moment (since that's the largest one made), but it can handle up to 2TB once they make a card that large.