How high should Res be in system?
 

This may be a stupid question, but I'll ask anyway as I haven't seen it asked yet. As far as elevation goes, where should the reservoir or t-line be? IF it is the spot in the closed system that has an opening, my thought would be that the opening to either should be at the highest point in the system. IS this right or wrong? If it were lower than other components, would it not spill out when opened?

would not spill out

if water spilled out of the tube, air would have to replace the said water that left

how will this happen in a (truly) closed loop?

think cup of water with index card and all is clear

Thanks. I have some left over acrylic tubing and am planning to make my own reservoir. That will help me decide on placement. ;)