I assume that you meant “baking” the fluid simulation, rather than “rendering”.
You have a Subsurf modifier on the fluid domain that should be deleted prior to
baking (You can add it again after baking if desired).
Also, your fluid obstacle / box’s inner walls seem to have a strange slope to them.
This usually happens if you use the Solidify modifier without the “Even thickness”
option. For a simple object like this it is just about as fast to use extrude. Just
make sure to do a “recalc normals” to ensure all the normals are pointing the right
In a case like this, I would just forget about the box obstacle, and use the domain
as the container, since the fluid won’t go past the bounds of the fluid domain (and
then add the box later by making the inside of the box even with the side of the fluid).
This also helps to avoid little droplets of fluid from landing on the edge of the box,
which tend to “jump about” and just looks terrible in the final animation.
(You can see this issue in the blend file I post below, when you bake it; and then
render the animation).
Although it doesn’t seem to cause an issue in this instance, you have a few unapplied
scales and rotation on your fluid objects. Press [n] to bring up the Properties
sidebar and look the the scale and rotation values. It’s best to keep scale = 1,
rotation = 0. To apply the scale and/or rotation, press [Ctrl]+[a] > Scale or
(Rotation & Scale) as required.
Finally, a low poly version of your inlet pipe set up as an fluid obstacle object
would be a good idea to prevent the fluid from intersecting the pipe.
Here’s the blend file after I made a few modifications:
(You just need to bake the fluid simulation)