Im building an oil/water cooled setup. The idea is simple: invert the motherboard, place only GPUs in the oil bath, pump the oil through a cooler, and in my case, the cooler will be placed in the filter of a large pond.
I have been doing experiments with an old frying pan and aquarium pump and an oil cooler. Lessons learned so far:
- mineral oil here is difficult to find at reasonable prices. I am going to use vegetable oil and replace it every year if needed.
- As expected, the aquarium pump (even though a very powerful one at 1600L/H) was utterly inadequate. I gave almost no flow when the oil was cool, only at ~60C+ did the oil become fluid enough to generate some flow, but still way too little. I ordered this:
http://www.ebay.co.uk/itm/New-12V-DC-CPU-Cooling-CAR-Brushless-Water-Pump-DC50C-1240-High-performance-/120828500685And I hope that will work better (4m pump head is a fair amount) because the others need 24V and thats no so easy to generate at those amps. 12V can be powered by a PSU. If its still not enough, Ill may just add more.
- air cooled, my small radiator was completely unable to cope with the 1750W frying pan. That too was expected. Submerged in cool water it seems like it should work, although I have yet to generate high enough oil flow to be sure.
- reinforced garden hoses seem to work fine, even at 60+C they didnt become weak. They are cheap (I have to run them a few meter distance to the pond). Dont use clear tubing if you opt for vegetable oil, sunlight is the prime cause for oxidization (=oil going rancid), far more than humidity or air.
Ill post some pics later when the pump arrives and I begin testing with an actual rig.
). Having a giant water sink as the terminal source would make things much easier. 
