Several updates since writing the post:
- I have gone back to air cooling — I suspect I wasn’t getting enough water flow velocity through the system as I had too many junctions and loops — the system reached 80 degrees C one night and next morning all the colour dropped out of solution and a (moderately) high pressure gas had formed in the loop — this lead to some leakage at serveral fitting connections. Fortunately only a bit of water leaked onto a HDD all was OK. However the chemicals in the pre-mix solution smelled really nasty.
- I would’t use any pre-mix or dyes in a loop — based on my experience above these can be really nasty smelling chemicals (presumaby pretty toxic), and if dye drops out of solution, can leave a hard residue in waterbloks, radiators and tubing that cant be flushed.
- I would only watercool one or two GPU’s. To watercool 3+ 250W GPU’s takes a lot of planning and testing and hard to balance radiator space+fluid velocity for system to work well.
- I am now using a HAF932 coolermaster case for air cooling 3x 250W GPU’s. Using negative airpressure has been key. With the HAF932 you can run a large fan in exhaust mode at the side of the case (exactly opposite the tops of the GPU’s) which draws out significant heat comming off the 3 standard air-cooled GPU’s. (The HAF932 is an old but excellent case, they dont seem to make cases this solid anymore).
- Watercooling took a lot of time to get working, was fun, but now that I am just running fans I am a lot less concerned about leaving my machine to run for days now and just need to turn on the air conditioner in the room on hot days.
- The noise from the air cooling system is on par with my watercooling rig — the Noctua NF-A14 industrial PPC-2000 PWM fans I was using for a radiator was pretty loud, now the main source of noise is the GPU fans.