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1 1/2" split to 2 3/8"???

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New Member
Mar 20, 2002
First of all HEY EVERYONE I'm new to the forums. :D :eek: :D

My first questions is this: I'm building a water cooling rig that requires a main 1/2" hose. However, i'm splitting it into two, 1 for GPU and 1 for CPU. I'm using the Gemini cool cpu and gpu waterblocks which require 3/8" hosing. So if i equally split the 1/2" hose into two 1/4" hoses, that would work fine I'm sure. But i'm wondering if when I split a 1/2" into 3/8" hosing if the two 3/8" hosing would fill fully or would just be partially full? I'm new to this, as you can see, and would really appreciate any help I can get! Thanks in advance! :burn:



Underwater Senior Member
Nov 29, 2001
Hey Nikolan, Welcome to the forums!

In a closed water system, there should be no air left inside of the tubes. This is accomplished like in the attached picture. The water returning to the reservior, would sweep the air from the tubing where it would flow up to the surface in the reservior. This keeps the pump pumping only water into the system, and the air constantly being removed until there is none left.

It's the same idea with a "T" fitting/tube idea. The tube acts as a reservior would (only a bit slower).

Have fun, and enjoy!

Koooler King

Nov 21, 2001
North America
If all tubing were of equal length, all fittings the same, and both cold plates were identical, etc. you would get 50% of the flow to each. In practice, however, one flow path will have lower resistance and would get the bulk of the flow, leaving the other wanting.

To ensure balance, you should put them in series so you guarantee full flow to each. If one device is more tempurature critical, put that first in the flow path. Overall, you still have the same amount of heat being taken away, so other than slightly higher temps at the second chip, this should not be a problem. Good luck.

Koooler King


Feb 22, 2002
I don't think that it would dramatically reduce flow that much. In fact, it would probably take some strain off of the pump due to the back pressure in a single path system.
I've noticed, that when I have my pump at 250, and when I have it at 400, I don't get nearly the equivelent amount of flow the change would indicate. Probably only 10gph more, maybe.
I think this is due to the back pressure, so if you have a good enough pump, and you're not pumping that high, you should have no worries.