Personally I would imagine that water coming right out of the rad would be cooler than water entering the rad. However there are many discussions about this and people think that loop order doesn't matter. Following are 2 orders I could go with:

1) Res - Pump - 120mm Rad - GPU 2 - GPU 1 - 120mm Rad - CPU - 360mm Rad
2) Res - Pump* - 360mm Rad - 120mm Rad - CPU - GPU 1 - GPU 2 - 120mm Rad

*The pump will be at the side of the res although the res will still be slightly higher. I'd need to tilt the casing to make sure water is being fed into the pump by gravity when running the loop for the first time.

I am also considering adding a 3rd GPU in the future.

1) Provides possible the shortest route but the difference would only be about a ft.
2) Provides what I believe the coolest water to the CPU first. A little inconvenient because I need to tilt the case to avoid running the pump dry.

Which is the better loop to go with? I am concerned about #1 because the GPUs can get very hot.

Loop order does not impact temps at all.

Regardless of any order in the end the whole loop will reach its thermal equilibrium.

Loop order only matters for a few things:
- amount of tubing used (length); directly impacts pump head pressure
- loop order doesn't cause your pump to draw air; hence why most suggest reservoir -> pump order
- aesthetics, ease of routing, avoiding kinks

as long as not too many elbows, pump behind reservoir, no kinks its good to go...

kinda agree with owikh...

There are some places where I could use 90 degree elbow. A 3 way rotary is quite costly and takes up quite a bit of room. My third gpu's fitting may be touching the bottom of my casing if I went with 3 way rotary.

now only i know, got a few 90 degree in my loop. can i replace it with dual rotary..? is it gonna be any better

This post has been edited by kakicam: May 24 2011, 12:43 AM

Just get a Swiftech pump and it has no problems running on a few water blocks and 2 radiators. No big deal on the loop or rotaries you're using. If the water temp is 100C, moving faster doesn't make it cooler. This is science

just asking, what pump are u gonna use initially..?