i'm going to fill up the loop now the 3th pump is installed, own mixture : 25% Ethylene Glycol and 75% PURE water, no demi.
what you see in the measure cup is the Glycol no color pure 100% glycol :

here my koolanc poor in cup on the ZERN res with a snake connector to make it a little bit eassier to fill :

on the drain valve i putted also a tube in a bus filled with my mixture, where the pump can draw it's liquid from when i put the valve open, to make it a little bit eassier to lol :

and here comes the first liquid lol, pumps are now running to get the last micro bubbles out the loop, for now, no leaks found :