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Dual water pump control help needed

W

watercooler

n00b
Joined
Mar 18, 2025
Messages
45
Hi everybody, i'm finally planning on doing my first watercooling build, and i'd like to have 2 pumps running at a low speed, but if one pump fails, and the temps start to rise then the pump speed will be increased so the pc will still be cool running until I replace the pump.

I like the look of the Thermaltake D5 pump+res units, but I have no idea if they would work well together if one pump died? Both pumps would be at the same level, which I assume would help if one were to die?

My other big worry is that if the dead pump is still receiving power, is that going to get hot? My guess is that it will warm up but hopefully not anywhere near enough to start melting plastic or anything like that?

I don't know if this speed control would be ok from just from mobo fan speed and temp monitoring?
I'm happy to source pump power direct from PSU and route signal wires to mobo.
Or is it better to use a controller such as AQUAAERO 6 ? I like this controller because it does not rely on software to operate.

Any help much appreciated!
 
Two pumps, too complicated and you are overthinking it
Stick with the simple stuff first. Then, when you have experience you can get more complex stuff.

I have a waterpump that still works after 12 years. Just buy a good quality one.

Geez...
 
To reiterate what Leslie said, don't overthink it. Just get a good quality D5 or DDC pump and run it at full speed, control isn't necessary. What is necessary however is proper decoupling from your case with rubber bushings, which will do wonders to reduce pump noise. Also make efforts to get the pump some cooling, whether through direct airflow or a heatsink style case, especially a DDC. My DDC is 15+ years old with tens of thousands of operation hours, and runs like a champ. All I've ever done is NOT run it dry, and swapped out the plastic housing for a metal housing with a finned base. Heat kills pumps over time and running them dry damages them instantly.
 
12 years! What brand is that? Is it quiet?

DDC, metal housing, 15 years.
I'm gonna check that out, sounds awesome!
 
Get PWM pumps and have your motherboard control them based on whatever temp sensor you feel like using (CPU most likely, maybe external temp sensors if your motherboard supports it).

I had one D5 die on me after about 12 years of service in my system, and at least 5 years prior to my acquisition of it.
 
I don't trust Tt. They have a long long history of shoddy products, copyright infringement and horrible customer support. If you don't believe me google
Thermaltake copyright infringement" and "Thermaltake customer support good or bad"
 
Don't let it cavitate either...it shreds impellers. I've roasted a few impellers. In my day job, we have shredded impellers on 100+hp pumps with cavitation.
 
How about Aquacomputer:

https://shop.aquacomputer.de/Water-...or-with-PWM-input-and-speed-signal::3255.html

But if I want the fancy fountain effect reservoir on the pump, it looks like I still need to get this pump adapter to make it fit:
https://shop.aquacomputer.de/Water-...-compatible-with-aqualis-base-G1-4::2925.html

https://shop.aquacomputer.de/Water-...tand-Alone/aqualis-ECO-450-ml-G1-4::2912.html

I didn't see any noise level specification on the website, but a pump like this on soft rubber mounts should be pretty quiet correct?
 
Agree with applegrcoug, don't let pump cavitate.
Cavitation occurs when the liquid in a pump turns to a vapor at low pressure. It occurs because there is not enough pressure at the suction end of the pump, or insufficient Net Positive Suction Head available (NPSHa). When cavitation takes place, air bubbles are created at low pressure. Cavitation can also occur when air bubbles collect in pump when there is no pressure issue. This is why most custom water cooled systems mount pump low in case, often at bottom of case.

Agree with pendragon1, keep it simple.
KISS = Keep It Simple Stupid
Build it simple so there are less chances for problems to occur.
 
OP, don't listen to these n00bs. :jimlad:

Cavitate all the way!!!

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Ok, another noob question.
If the pump is mounted at the bottom of the wc loop, and has a reservoir attached above the pump, which is aways kept full, then cavitation would be impossible correct?
 
watercooler said:
Ok, another noob question.
If the pump is mounted at the bottom of the wc loop, and has a reservoir attached above the pump, which is aways kept full, then cavitation would be impossible correct?
Click to expand...
Technically speaking, a completely full reservoir would have a higher chance of having cavitation than a reservoir with some air in it. The pressure drop due to contraction will be less with an air buffer, but for the most part it won't matter in a standard computer watercooling system.

Aquacomputer is good and reputable. I also like Watercool products.
 
Tsumi said:
Technically speaking, a completely full reservoir would have a higher chance of having cavitation than a reservoir with some air in it. The pressure drop due to contraction..
Click to expand...
I think I know what you mean, so it's like the pump+res combo would need a vented diaphram to allow pressure equalization, or just have some air at the top of the res which can expand and contract.
 
While pumps can have cavitation caused by pump not being able to draw water into itself, what most common "cavitation' heard is not really cavitation, but air bubbles flowing into and being trapped in pump. Custom loops with pump at bottom of system and reservoir above them rarely if ever cavitate. If they do it's caused by restriction in line from reservoir .. like plugged filter / strainer, collapsed hose, etc.
 
Agreed with most of the above.

I wouldn't bother with two pumps unless you need the static pressure like if you are running multiple restrictive radiators or filters.

The redundancy is nice but short of getting an occasional dud pump or you abuse it like running it dry, DDC and D5 pumps are insanely long lasting.

I have a DDC_2 18w pump I bought in 2006 that still runs. I only stopped using it because it started to get a loud.

In regards to controlling the pump. Both the DDC and D5 style pumps are available as PWM and the head can be used on any motherboard fan header for speed control. However unless you have an extremely quiet case/fan set up or the fan is right next to your head, most people probably will not hear it even at 100%.

I use an aquacomputer Quadro controller to controll my fans and pump (a Aquacomputer D5). However the pump is either at 100% or 50. I have my settings so when the PC is idle the pump drops to 50% and fans to a low rpm. That is only because I am sensitive to the frequency of the sound the D5 pump makes. I cannot hear it when the fans are up to speed.

Keep your pump low in your loop and you will be fine.
 
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