How do I select a water pump

[1234Shawn]

I am working on my first water cooler build and need some help selecting a water pump. I would like a quiet build. I plan on cooling my GPU and CPU with a 280mm radiator. I'd like to put the res and pump in some of the 3 avalable 5.25 bays. However, I can mount a pump on the bottom of the case. In the future I plan on OCing the GPU and CPU. I may need to add more rads and can fairly easly add 1 or 2 140mm rads.

Sould I just pick up whatever 35x pump? I've read they are quiet, but unsure what limitations they have.

From what I have read so far it seems I need to determine the resistance of my unit and and have a flow rate of 1 to 1.5 GPM. Is this true? If so, how do I calculate this and then, use that information to select a pump?

 

[gilbadon]

That is a fairly easy system to pump water. There are 2 things to consider when buying a pump. Head pressure and flow rate. If you know anything about electricity, it is like voltage vs current. You need enough voltage (head pressure) to push the current(flow rate) through the resistor (system resistance).
Head pressure is more important than flow rate. You want at least 1GPM of flow when your system is running. There are pressure vs flow rate curves that show the flow rate at any given pressure.

http://www.xtremesystems.org/forums/showthread.php?257721-Skinnee-Labs-The-Pump-thread...

Look at the curves and determine which one at your system resistance will work for you.

I will also recommend going to Aliexpress.com and looking at winfmod's store. Really cheap and high quality products that will do things quietly and well. I am not a sponsor, just a fan.

 

[1234Shawn]

Giladon,

Thanks for your quick reply. I've seen alot of these curve charts. I guess my problem looking at them is I dont know what my systems resistance will be.

 

[gilbadon]

Check this out:
http://www.overclock.net/t/1108918/what-can-my-pump-handle-a-guide

 

[1234Shawn]

So for my set up Id go 0.9 gpu, 0.9 cpu, 0.75 rad (380mm now and 2x140mm in the future) and, 0.5 tubing for a total of 3.05?

Then I look for a pump that will do 1 gpm at that pressure?

 

[gilbadon]

Exactly! You got it. You may have to do conversions between pressures and flow rates to determine if a pump can do it or not.
Head pressures may come in mH2O or mmHg or Pascals.
Flow rate may be in L/s L/min G/hr G/min.
Just use google to convert =)

 

[1234Shawn]

There are curve charts for various rpms as well right? So i can go quiet at lower speeds? Are pwms good for this?

 

[gilbadon]

Well, yes, but if you get a good pump, you will not even need to reduce it from 100% because you will not hear it. A D5 pump or 35X pump is dead silent.

 

[1234Shawn]

Those were the two pumps I was debating between. I have heard the D5 is quieter larger and has less pressure/more GPM vs the 35x which is smaller louder hotter with more pressure/less GPM.

 

[gilbadon]

Those were the two pumps I was debating between. I have heard the D5 is quieter larger and has less pressure/more GPM vs the 35x which is smaller louder hotter with more pressure/less GPM.

Both will do great. The D5 is the better pump though. The D5's curve is a ton better because as system pressure increases, the flow rate does not decrease as much. As for the 35X, the flow rate decreases very quickly as system pressure goes up.

My debate is that you only need a 35x when room as at a premium or you want a sleeker looking pump/res combo.

 

[1234Shawn]

I expect my system pressure to be 3.05psi. 0.9 cpu block, 0.9 gpu block. 0.75 3x radiators, 0.5 tubes. The graphs I look at show the d5 needs to be ran at setting 4 or 5 for a system with my pressure. The 35x seems to handle twice that and I expect I can run it at half speed. I am a noobie so please corrext me if I am wrong and/or shoe me a better graph for a d5 pump

 

[1234Shawn]

... I was expecting the 35x at halfspeed would be quieter than the d5 at 4 or 5?

 

[gilbadon]

... I was expecting the 35x at halfspeed would be quieter than the d5 at 4 or 5?

Both will be good. You are right. There are different models of D5 and 35X though. Not all DDC (35X) pumps outperform D5's to head pressure though.Some are better than others.

http://www.swiftech.com/MCP655-B.aspx#tab2

Under the performance data tab, notice the graph.

1 Gallon ~= 4 Liters
3.05 PSI ~= 2.1 mH2O

I would do whichever is cheapest TBH.

 

[gilbadon]

Check this pump out: http://www.aliexpress.com/store/product/Water-cooling-water-pump-12V-14W-Maximum-head-5M-free-shipping/907279_510261352.html

It should power your system well. There are limited reviews on it because it is chinese, but I have heard good things from those who have used it. That store has all sorts of water cooling parts for STUPID cheap too. Their fitting prices cannot be beat!

 

[rubix_1011]

I would be cautious about purchasing components that are unknown and typically untested in a market where testing is of highest importance.

Both D5 and MCP35x are excellent pumps and both perform very similarly. Flow rates are very nice, but there is often the expense in a loop where restriction and pressure drop can impact the flow curve whereas a higher head pump would likely overcome more restriction on the flow curve and maintain better flow rates.