Serial loop Vs. Parallel loop

[toolmaker_03]

a detailed parts list, of the two water loops used in this test setup.
2 MCR320-QP 360mm radiators
http://www.swiftech.com/MCRx20-QP.aspx
2 EVGA GeForce GTX 580 FTW Hydro Copper 2
https://www.evga.com/articles/00592/
1 XSPC raystorm CPU block
http://www.xs-pc.com/waterblocks-cpu/raystorm-cpu-water...
1 swiftech MPC655 pump
http://www.swiftech.com/mcp655.aspx
6 corsair SP fans
http://www.corsair.com/en-us/air-series-sp120-high-perf...
6 bits power 3 way 90's
http://www.frozencpu.com/products/12084/ex-tub-744/Bits...
1 Y block
http://bitspowerwork.com/html/product/pro_show.php?prod...
1 250mm reservoir
http://bitspowerwork.com/html/product/pro_show.php?prod...
8 3/8ID 1/2OD compression fittings
http://bitspowerwork.com/html/product/pro_show.php?prod...
2 T's
http://www.xs-pc.com/hose-fittings/g14-t-fitting-black-...
5 male to male fittings of varying length
http://www.xs-pc.com/hose-fittings/g14-5mm-male-to-male...
4 female to female fittings of varying length
http://www.xs-pc.com/hose-fittings/g14-18mm-female-to-f...
2 koolance flow meters with display
http://koolance.com/ins-fm19-coolant-flow-meter
http://koolance.com/dcb-fm01-flow-meter-adapter-with-di...
1 loop filter
http://koolance.com/ins-fltr03-inline-coolant-filter
2 temp sensors
http://www.frozencpu.com/products/10373/ex-tub-620/Bits...
1 alphacool bubble down
http://www.frozencpu.com/products/17333/ex-tub-1558/Alphacool_Bubble_Down_G14_Thread_Reservoir_Flow_Regulator_-_Deep_Black.html?tl=g30c97s169
1 bitspower aqua pipe
http://www.frozencpu.com/products/11863/ex-tub-713/Bitspower_G_14_Silver_Shining_Aqua-Pipe_I_BP-WTP-C17.html?tl=g30c97s169

This system is overclocked, on both the serial and parallel test setups.
CPU overclock @ 4Ghz
GPU1 overclock @ 850Mhz
GPU2 overclock @ 850Mhz
Memory overclock @ 1600Mhz
CPU stock @ 3.2Ghz
GPU1 stock @ 772Mhz
GPU2 stock @ 772Mhz
Memory stock @ 1333Mhz
this is the serial loop setup and what it looks like, and here are the hardware temps at idol, ambient temp of the room is at 28.6C
CPU 43C
GPU1 37C
GPU2 37C
the water temps at idol are
29C-30C
the hardware temps at load are
CPU 61C
GPU1 51C
GPU2 51C
the water temps at load are
37C-38C
the delta t of the system at load is 10C
http://imgur.com/Gi4wFZO,G1Mte0g,Pb8ot4j,k8LlLK5

this is the parallel loop setup and what it looks like, and here are the hardware temps at idol, ambient temp of the room is at 28.6C
CPU 43C
GPU1 35C
GPU2 35C
the water temps at idol are
29C-30C
the hardware temps at load are
CPU 57C
GPU1 46C
GPU2 46C
the water temps at load are
34C-35C
the delta t of the system at load is 7C
http://imgur.com/pBZY5ne,yIT8rwA,CgNlfyH

this is the difference between the hardware used on the serial loop, and the hardware that needed to be added to the parallel loop.

http://imgur.com/U3yYYJl

 

[toolmaker_03]

I think I can explain the reason for using two hoses that are going into the top of the reservoir, I use to have a tube line from the bottom of the reservoir to the pump inlet, and I did not change this until my water loop was going fast enough that the vacuum on that line started to collapse the tube, so to fix this I attached the pump to the bottom of the reservoir with a small 5mm male to male fitting, by doing this all I really did was move the issue to the hose at the top of the reservoir that split to the two radiators, so I removed the Y, and I thought to myself, is there enough vacuum to collapse the two hoses coming out of the two radiators at the same time? the answer is no, there is not enough vacuum to collapse them both at the same time, so now the system can flow faster as a result of not being vacuum locked by the tubing. I am sure that there are other ways of fixing this issue like using rigid tubing, or soft copper tubing. but this is how I thought might work, to solve the issue at the time.