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Watercooling: New Idea for plumbing? Series vs parallel

Last response: in Overclocking
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November 12, 2006 8:16:08 PM

So which is the best way to set up a water cooling loop ?

parallel:
...............................................................................
......................|-----[gpu]-------|..............................
.|---[pump]----| .......................|----[radiator]----|...
.|....................|-----[cpu]--------| ........................|...
.|---------------------------------------------------------|...
...............................................................................

( sorry about the dots.. the forum removes spaces)
or series:

|---[pump]--------[cpu]----[gpu]----[radiator]-----|
|-----------------------------------------------------------|

The advantage of 'in series'
higher water flow through each device so better cooling for the first device
disadvantage:
seccond device in the loop doesn't get cooled well because it gets already hot water from first.

The advantage of parallel:
both devices get cold water
disadvantage:
slower water flow through each device (as the pump pressure is split to 2 feeds) so maybe less cooling but cooling is balanced.

It seems parallel would be technically the best, but looking at photos of most WC rigs they appear to do 'series'. Anyone have a clue why?
Could it be that no-one has actually thought about it and series is just easier to set up?
November 13, 2006 12:09:33 AM

A series setup is much easier to impliment as it involves less equipment and, therefore, less space used. I deally, if you had a series setup where you had a rad after each waterblock (I am speaking of just the CPU and GPU here) then, as long as you optimized your loop (i.e. mcp655 pump, 1/2 id tubing, for example) you should see good results.

Whenever I had a case where I had to set up two parallel loops (such as when I had two peltier water blocks - one for the CPU and one for the GPU) I ended up using two mcp655 pumps for each loop. Their only common ground was the resrvoir where they met.
November 13, 2006 7:14:01 AM

Quote:
...
It seems parallel would be technically the best,.

The problem with parallel w/only a single pump is that in practice it is very difficult to get equal water flow through the two branches. If one branch ends up with more resistance to flow than the other, you can end up with most of the flow going through one branch, leaving the other branch uncooled, and no obvious sign of a problem.
Thus, parallel with one pump per branch is best. However, pumps get expensive, so people go with series.
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November 13, 2006 7:59:14 AM

Quote:
So which is the best way to set up a water cooling loop ?

parallel:
...............................................................................
......................|-----[gpu]-------|..............................
.|---[pump]----| .......................|----[radiator]----|...
.|....................|-----[cpu]--------| ........................|...
.|---------------------------------------------------------|...
...............................................................................

( sorry about the dots.. the forum removes spaces)
or series:

|---[pump]--------[cpu]----[gpu]----[radiator]-----|
|-----------------------------------------------------------|

The advantage of 'in series'
higher water flow through each device so better cooling for the first device
disadvantage:
seccond device in the loop doesn't get cooled well because it gets already hot water from first.

The advantage of parallel:
both devices get cold water
disadvantage:
slower water flow through each device (as the pump pressure is split to 2 feeds) so maybe less cooling but cooling is balanced.

It seems parallel would be technically the best, but looking at photos of most WC rigs they appear to do 'series'. Anyone have a clue why?
Could it be that no-one has actually thought about it and series is just easier to set up?


I now use parallel. I use the Polarflo E waterblock. Until a recent motherboard change I was cooling mobo chipset (north and southbridge), GPU and CPU all with water. My pump is a 600lph Eheim and it couldn't cope with the long tubing (reservoir and rad are outside case). There was too much back-pressure on the pump and it became noisy. So I sat down and drew a parallel loop on paper, re-plumbed my water system and it worked perfectly! No more excessive loading of pump! My Polarflo E uses 1 x inlet and dual outlets.

There is a single 1/2" inlet tube from the pump/reservoir running to the CPU Polarflo inlet, the dual outlets from the polarflo E, each go to different blocks (GPU/Chipset) and the most important feature is that the dual outlets finally go to the custom reservoir (rather than combining to a single tube). So my reservoir has 1 x outlet from the submerged pump which goes to CPU, it then splits into 2 for the chipset and GPU and it goes all the way back to the reservoir as 2 lines. Cooling performance is great for the GPU and chipset as well.

Feathers
November 13, 2006 8:49:33 AM

i would use the parrallel however i would (assuming your water flows left to right) swap the radiator and pump around. not that it would make much of a difference i would just prefer the water going straight from the radiator to components not via the pump
November 13, 2006 9:07:23 AM

Me too. Some pumps can add heat. I use a submerged unit myself. I used to own a tiny C-Systems pump which ran very cool.
November 13, 2006 3:48:24 PM

Quote:
i would use the parrallel however i would (assuming your water flows left to right) swap the radiator and pump around. not that it would make much of a difference i would just prefer the water going straight from the radiator to components not via the pump


Oh yeah. good thought. Thanks.
!