I've posted these pics before but since inadequately secured tanks seems to be such a common issue I'll post them once again ...
When I first brought our new 2014 Coachmen Freedom Express 192RBS home and filled the fresh water tank it sagged noticeably ...
... so I asked my dealer to install a couple of steel supports under the tank which eliminated the sagging and ensured the tank couldn't fall off ...
In the two years we've now owned this trailer and traveled many times with a full tank I've never had any issues at all. It seems such an obvious solution one has to wonder why trailer manufacturers are so reticent to properly secure these tanks in a similar fashion at the time of manufacture. :h