pump noise D5

A

allen5055

[H]ard|Gawd
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Mar 25, 2012
Messages
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I have a dual D5 pump/reservoir. I have kept the pumps running on 5 for years. My fans were Gentle Typhoon AP-15s and pretty loud so I've never noticed the pump noise. Recently I replaced all my fans with Noctua AF-12x25s and now my computer is very quiet so for the first time I can hear the pumps. I noticed one of the pumps makes a faint oscillation sound at 5, and when I turn it to 3 it rattles, and when I turn it to 2 I can't hear anything. It may have been making this sound the whole time I've had it (7 years?) but I've never been able to notice because of the fan noise. I haven't seen any debris in the loop in all the times I've changed the water.

A few questions:
1.Does this oscillation sound indicate a problem?
2. If I have one pump on setting 2, can the other pump remain at 5 or should they both be the same speed?
3. What speed should I leave my pumps on?
 
I'm having a difficult time assessing it without hearing it, but yeah, pumps do make noise even when new. If it is particularly bad it could be indicative of a problem, but otherwise it is just normal.

You can try to minimize it by decoupling the pump from the case as much as possible. You can use rubber bushings, or any number of methods for this.

I did, and never got mine quiet enough for my liking, so I switched out the pumps for pwm controlled units, and now use my Aquacomputer to only crank up the pumps when necessary based on loop temp.
 
Disclaimer - I have never worked with a custom water cooler but know a bit about fluid dynamics and mechanics.
What kind of pump do you have? In case it is a centrifugal pump it could air bubbles or a bad bearing. On a positive displacement pump it could be a broken rotor (or how ever they are called) or also the bearing.
If the pumps are in parallel or two independent cycles it shouldn't be a problem running them on different speeds. Although I would suggest you to further investigate the cause since you would not like a pipe failure as a worst case scenario :)
 
The pumps are in parallel it is centrifugal spin. The oscillation is very subtle. I destroyed a d5 pump by dry running it once and the vibrations were really obvious the whole case rattled.

Also, what speed do I need to run the pumps at? Maybe I should just put them both at 2?
 
allen5055 said:
The pumps are in parallel it is centrifugal spin. The oscillation is very subtle. I destroyed a d5 pump by dry running it once and the vibrations were really obvious the whole case rattled.

Also, what speed do I need to run the pumps at? Maybe I should just put them both at 2?
Click to expand...

Do you have a flow meter? If not just run some tests with pump speeds at different levels. If you see an unacceptable increase in temps with both pumps at 2 while gaming or while your rigs underload then you know you have dropped to far below the ideal 1gpm and need to increase your flow. If not, rock on ;)
 
Thanks for the advice. I was reading about D5 pumps and it does seem like all of them have some noise at 40%+ speeds and some are noisier than others. One of mine is definitely more silent than the other. This is the first time my computer fans have been quiet enough for me to hear the pumps.
 
allen5055 said:
The pumps are in parallel it is centrifugal spin. The oscillation is very subtle. I destroyed a d5 pump by dry running it once and the vibrations were really obvious the whole case rattled.

Also, what speed do I need to run the pumps at? Maybe I should just put them both at 2?
Click to expand...

The general rule of thumb is that you want a minimum of 1 GPM to make the most of your loop. You can gain some improvement in temps above that, but the returns generally are rather diminishing.

It's impossible to say what setting to run the pumps at to accomplish this, as blocks, radiators etc. all have different resistance and it also depends on your routing of your tubing. If you don't have a flowmeter, as has been suggested above, you can arrive at adequate flow experimentally, by putting a known load on the thing and a known fan speed and adjusting the pump speeds until you find something you are happy with.

Just remember to give it some time to settle in after each adjustment.
 
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