Differences between 3/8" ID and 1/2" ID tubing?

Emission

Supreme [H]ardness
Joined
Dec 6, 2005
Messages
4,420
I've been using 3/8" ID tubing in my system without issue for a while now, and I've been curious all along if moving up to 1/2" ID tubing would provide a noticeable improvement in performance. My setup is listed below:

- DD-CPX 12v Pump
- Swiftech MCRES-MICRO Reservoir
- Thermochill PA 120.2 Radiator
- Enzotech SCW-Rev. A CPU Block
- Swiftech MCW60-R VGA Block
 
Last edited:
As with almost everything computer related: "It depends on your exact setup"

However, it doesn't really matter in practice. From what I remember when I was reading up on things it's simply a balancing of effects. Think about the pV=nRT equation for pressure, volume, and temperature. Changing diameter of tubing changes other factors like flow resistance and flow speed. Generally, unless the diameter of your tubing is so restrictive that it's hindering your pump(Not going to happen in a reasonable setup), the flow speed will lower with wider tubing.

Water cooling setups are systems. Changing one variable tends to affect all others. You have to consider the thing as a whole and make a decision for yourself. Does your Radiator work better with higher water flow? Is the water taking enough heat from your cpu block at the given speed? etc etc.

Short Answer:
I wouldn't invest more in new tubing just to change size. Unless you currently have a problem
 
Assuming your pump is up to the task 1/2" ID tubing will increase the volume of water moved through your loop over a given time period. It will also increase the volume of water in your loop as the increased tubing size will hold more water. For a simple loop I don't think it would make more than a degree or two difference because the volume of water won't increase by enough to make a significant change.
 
untouchable is mostly right....but...

The volume of water will generally stay exactly the same regardless of tubing size. There is a negligible change.

Your pump is controlling exactly how much water is moving through your system.

Same pump bigger tubing = slower water speed; Same volume -- moving through system
Same pump smaller tubing = faster water speed; Same volume -- moving through system

The only time water volume moved through your system would change when you change the size of the tubing is if you dramatically alter water flow restriction:
By moving from tubing that was way to small for your pump to begin with to reasonable tubing.
Or By moving from tubing that was reasonable to tubing that is way to small.

Neither of those situations should happen when dealing with an already reasonable setup:)
 
My college roommate is a computer engineer and we talked about this quite a bit at one point in time. He was using 1/2" ID tubing and got tired of dealing with it. I was running 3/8" ID and we both ended up going to 1/4" ID for it's ease of use. Between the 1/2" ID and the 1/4" ID there was only a 1-2 degree C difference. It does depend on the exact setup you're running. He was running an AMD quad and a 4890 on a 3x120 rad without any problems at all. As the restriction comes primarily from blocks, not the tubing, it really doesn't seem to make too much of a difference what the diameter is. I'm still running the 1/4" on my Q9550 and GTX275 with no problems at all (see sig for temps).
 
My understanding of the system overall is that depending on the flow speed, the water has more or less time to heat up in the blocks and cool off in the radiator. My pump runs a bit undervolted as it is, and my temperatures are very decent. Well, thanks for the input guys, much appreciated.
 
On modern systems its irrelevant unless something very strange is going on. Minimal and likely unmeasurable (withing the error of the measuring device) improvement going from 3/8 to 1/2 ID tubing on a decent loop.
 
As I predicted, the test results show a 1 Celsius difference between 1/4" and 1/2" tubing being the greatest possible difference. Well, that just makes my life easier. It would cost time and money to convert the system, which is just a pain in the ass, considering the non-existent gains.
 
"Running the above range of tubing/fitting sizes through the optimal pump power estimator software I wrote, it predicts that the best pump to use is one that's consuming around 10-13W, with optimal pumping efficiency in the ranges of 3-6LPM. I won't go into the intricacies of the pump power estimator. It's not an exact science, suffice to say that it looks at the wholistic scenario given a waterblock, heatload, room C/W, radiator, system restriction, and so on, and puts out a suggestion for where the optimal range of pumping power lies for that setup. This allows us to then pick a real pump that closely matches the suggested pumping characteristics."

Hmmm, so it this not actually validated ... meaning any of the test cases actually setup & run to correlate empirical versus calculated. I had thought about that before, but it register with me.

I am not disputing, but I can't have religion for this either.
 
The heat capacity of water is high enough that the difference between 1/4" and 1/2" tubing is marginal in terms of temperature. I would only mess with my loop if I was making changes to the layout or the overall setup.
 
Back
Top