Plumbing

[FMuscle]

I have a few decisions to make about plumbing the coffin. One I'm facing right this second is the return. How to prevent siphon back?
I know of two ways, drilling a small vent hole at water level, or use a check valve. Which one would you use, and why (pros/cons).

I also want to add a chiller to the system. I'm running a sump, and the bloke at Vebas suggested a separate pump to take water from the sump, and return it to the sump, instead of messing around with the plumbing on either side. I like the idea, as I'll be having my heaters in the sump as well, but my question is, Where is the temperature sensor on a chiller? I have an external sensor for my heaters that will be in the tank, controlling the elements in the sump. Can I do the same with a chiller?  
I don't want the heater and chiller fighting each other because they pick up the temperature at different places...

Edited December 25, 2015 by FMuscle

[NoGi]

I'm assuming by your coffin journal that this was sorted?

[FMuscle]

I changed my temperature controller to one that does both heat and chill. But I'm still chill-less...