Do hot water tanks have to be in the drain pan
The purpose of a drain pan is to contain small leaks that can lead to damage and can give you warning that there is a problem. This doesn't mean that it is necessary, however for 10$ - 20$ at your local hardware store you could have picked one up - worth the small investment. (I'm surprised that a plumber who is called to install a hotwater tank doesn't have an extra pan in his tool kit)

The tank doesn't look level from the pictures. Try taking a level, place it on the top of the tank.

Here is a guide on how to level a hot water tank.


  New water heaters or water heaters that are placed on an un-level surface, need to be leveled and shimmed for them to work properly.


Personally, I would go pickup a new drain pan, call the plumber back and have the pan installed. If the tank is not leveled, he can address this at the same time.

The question you asked is whether this installation is safe - the tank will probably sit there without incident for many years. The problem I'm having is that if it is not level, you will be possibly shortening the life of the tank, could be voiding a warranty and are not protected in the event of a slow leak.