Water cooling system pressure

[marine73]

Building a custom cooling system with 3/8 and 1/2 inch tubing. Will probably use an Eheim or similar quiet
pump. Anybody know what sort of PSI readings to expect? I realize there are alot of variables with a custom system so I'm just looking for a range of values. Thanks

 

[stevennoland]

Your PSI is not as important as your flow rate. You can have a really high PSI and a crappy flow rate. Example: Taking a 1/2" outlet on your Eheim and then reducing it down to 1/8". More than likely your pump would have backflow probs. The restriction would be to great. The converse applies as well. Taking the same 1/2" outlet and expanding it to 1 inch. Your pressure drops along with your flow rate. Your pump is spinning it's wheels. The one thing I can recommend is if you do reduce the size (say 1/2" to 3/8") then re-enlarge after component cooled. I would really recommend you keep the size of hose and fittings all the same.

 

[marine73]

My intention is to keep flowrate above 170 or so gph. That should be sufficent as I'm cooling the cpu separartely from the gpu/chipset. Loops are combined at the res/through the pump/and then separate
into 2 cooling coils. Want to put a small gauge on the system and was trying to pin down a range, more for bling than anything else. thanks

 

[pelikan]

The flowrate will be determined by the PSI because watercooling loops are very restrictive. GPH ratings are useless for our purposes. Pump manufacturers rate PSI in terms of "head." The math goes like this: PSI x 1.33 = head. Head can be measured by pumping water straight up a tube. How high the water will go is the absolute head rating.
For a good flow rate you need a pump with at least six feet of head. The pump of choice these days is the Laing D4 (AKA Danger Den 12V Pump and Swiftech MCW-650). This pump has 10' of head.
The other thing to look for in a pump is power consumption. Roughly 75% of the power used by the pump will go into the water, heating it up. The Laing D4 only uses about 14W to produce 10' of head. The Eheim 1250 used to be very popular, but it uses 25W to produce only 6' of head so new, more efficient pumps are taking over.