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How to switch between power supplies for water pump

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New Member
Dec 30, 2017
Hi everyone!

I'm trying complete a water cooled system, and one of the main goals for this one is to make draining/filling as easy as possible. I'd like to be able to do the entire process without having to open the case at all.

I'm using a Corsair Obsidian 900D, and an EK-XTOP Revo Dual D5 (dual pumps).

So far I've got the perfect fill port in the top of the case, and the perfect drain port in the bottom back with the knob for the drain valve sticking out through a hole in the back. I can fill and drain without opening the case, except for one remaining issue. I need a way to wire up a couple of switches to mount to the back, and a nice pass through for the power cable for my external power supply that I use to power the pumps when filling.

My external power supply is something I picked up on amazon. It's basically a laptop brick with a couple molex plugs where it would normally plug into a laptop. The cable from the wall outlet connects to the brick with one of those little plugs shaped like a number 8.

I'm up for anything when it comes to getting the external power supply connector in the back of the case, whether it be a molex pass-through, or even mounting the power brick inside the case (it's a 900D after all, plenty of room even with four radiators). I'm open to suggestions.

I'd like to have two switches on the back. The first one would toggle the pumps between normal operation connected to the PSU, and powered by the external supply. The second switch would turn the power on/off for the external power supply.

Any ideas? Has anyone seen this done before? I could probably just buy some random switches and bust out the old soldering iron...and find some power plug pass-through thing online. But I'd rather use something made for this kind of situation that I wouldn't have to build myself...something higher quality designed by someone who knows what they are doing.

Thanks in advance!


N00b squad Member
Mar 3, 2005
Sounds like diy time. I'd suggest a dpdt switch to open the internal psu power circuit while closing the external psu circuit to power the pumps. That way, you can isolate the external power to only run the pumps and prevent inadvertently power other devices on the same rail.


New Member
Dec 30, 2017
Thanks corpsejockey! I took your diy advice and wired up a switch. I'm doing my leak test now and it's perfect!

Outside view of the panel:

Inside view of the panel:

View of the work in progress:


High Speed Premium Senior
Aug 5, 2002
Wow that is some setup with rads. Really like the idea of a second PSU / switch so you can run the pump for testing, without connecting/disconnecting anything else.

Bill Dimwit

Mar 21, 2018
Wow that is some setup with rads. Really like the idea of a second PSU / switch so you can run the pump for testing, without connecting/disconnecting anything else.

It would also allow the pump to keep running after shutting the system off. That would be nice when you want to shut the system off right after is was under a heavy load and was running hot.