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SOLVED - Ultitube 100 with D5 Next -> cavitating at >85% RPM / looking for advice

Sunday, February 7th 2021, 11:08am


I am asking for some advice regarding a cavitation issue that appeared when I installed a D5 Next pump with an Ultitube 100 and running the pump at >85% RPM.

I was using an Aquacomputer D5 Vario with fixed rpm in an Aqualis 150 without any issue, but on a whim I decided to try out those new stuffs and only changed the pump/reservoir in the loop.

My loop is made up like that : Pump in Ultitube 100 -> GPU -> 2x Corsair XR5 360 (slim rad) -> CPU -> Nemesis GTS 480 rad (slim rad) -> Pump and Double Protect Ultra liquid, with only 2x 90° fittings to avoid flow restriction.

Since the D5 Next is assembled with the Ultitube 100 there is cavitation when the RPM exceed 85%. Here is a video where we can hear it.
It is certain for me that it is cavitation because I can even see sometime micro bubbles rising from the Ultitube's integrated filter when this rattling sound occurs.

I am troubled because from the infos I gathered on the web about cavitation it seems that only very high power pumps or ships impellers are prone to cavitation.

As troubleshooting I tried :

the multiport lid for the Ultitube 100 using top inlet, same cavitation.
D5 Next in Aqualis 150, no more cavitation.
Another D5 Next, thinking that maybe the other was defect and might send it back, but same cavitation at >85% RPM.

Is the integrated filter the cause of the cavitation or is the Ultitube 100 reservoir defect ?

It doesn't bother me to use the pump in the 0-80% range as the flow is good enough to well cool components, I would just like to understand what going on.

I would be gratefull for any advice.

This post has been edited 6 times, last edit by "Tamuhelet" (Feb 15th 2021, 3:59pm)

Sunday, February 7th 2021, 12:38pm


Sunday, February 7th 2021, 12:54pm

Damn, all disappeared so had to write it all over again

Sunday, February 7th 2021, 12:56pm

Why does only one line show?

Sunday, February 7th 2021, 6:53pm


Why does only one line show?
Strange... I myself have problems when I edit my message to format the text differently.

Monday, February 15th 2021, 2:17pm

Here is a link to a video where we can here the cavitation.

I guess the loop is too restricive with the reservoir filter on top of that.

This post has been edited 1 times, last edit by "Tamuhelet" (Feb 15th 2021, 2:58pm)


Full Member

Monday, February 15th 2021, 3:05pm

It is normal to hear small bubbles work their way through the pump any time the loop has been recently re-assembled. That should go away after a few days.

Do you have any video that shows the coolant in the reservoir while this is happening?

Monday, February 15th 2021, 4:00pm


It is normal to hear small bubbles work their way through the pump any time the loop has been recently re-assembled. That should go away after a few days.

Yes, I have not mentionned that I am watercooling since more than 15 years so I am aware about that. The system is fully air bled, I have tilted the computer in every directions possible (not the pump upside down) to bleed the air and is running for 10 days now.

I do not have video showing the microbubbles, they appear and disapear very fast.

Sven from aquacomputer support contacted via email answered me that "a higher resistance of the loop could also cause such a problem."

I therefore mark the subject as solved.