In my Reefer (250), which uses a 500, I run the e drain into the rollermat’s water chamber. You should be able to zoom and see it here, it was also easier to pull the old sump and replace it with a 20L. Below that is a 1200 that is in my Max S500 that I did the same thing. Works great and takes up much less space then the union hack using the other side of the intake.
I think I need to look into setting something like this up on my reefer. At least then I’m getting 100% mechanical filtration when the water does start going down the emergency drain.