Mekanism-1.7.10-7.1.0.92
Forge 1205

I have a Railcraft Liquid Unloader that is moving Brine to a Dynamic Tank.

As you can see the tank is full

And the Liquid Unloader is full as well.

When I reconnect my pipe the Liquid Unload empties its contents to the already full tank.

Could you, while the fluid is draining, right-click on the tank with a Network Reader, please, and either post the output from it, or a screenshot? I'm unable to replicate this in development, so it's possible it's already been fixed.

The network reader is a great tool for figuring out if a bug is a bug. I did not know about it. Turns out that after the tank is full the pipe has an inventory as well and it has to fill up before the Liquid Unloader will stop dumping. I did not know the pipe worked that way. You can mark this one as solved but an update to the wiki might be a good idea. I saw nothing on it about pipes having an inventory.