Corsair 900D WC Build Log

consider going parallel on the GPU's iso Serial

RnRollie said:

consider going parallel on the GPU's iso Serial

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For?

Takes 400W to heat water 1C at 1.5gpm. Even at half that flow 0.77 gpm, takes 200W to heat water 1C. So serial, the water temp to the second gpu block is 1C higher worst case scenario. But usually load differences, waterblock contact differences will cause much more difference than 1C.

If you change to parallel, the only temps you improve are cpu temps by about 0.3C lower, because you increase flow of overall loop. GPUs are typically same, since now each gpu gets slightly lower flow as you split flow between 2 gpus, but both often little worse temps by 0.3 to 0.5C.

So temp differences mathematically and experimentally are nearly same, and typically much less than 1C, and all you accomplish is making the loop needlessly complicated, and risk uneven flow through 2 gpus.

ie, all risk, more complicated, ZERO gain.

And if you see more improvement then what is mathematically possible, it is from experimental error, which is all too common.

I've heard parrallel was the best solution when it came to GPU setups. The only serial configuration in the loop should be with multiple pumps.

rge said:

ie, all risk, more complicated, ZERO gain.

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Would you mind providing a basis for this? I don't disagree with you about the gains. I have run multi-GPU set ups both ways and as far as performance goes I don't believe that there is any appreciable performance difference, at least in my experience.

But risk? I really can't see that. For someone building a loop with multiple fittings, a pump, a reservoir, water blocks, radiators...etc, etc. A couple of additional GPU SLI fittings isn't going to make the build any more risky than any other build. Have there been confirmed and substantiated reports of uneven flow or temp problems from people running parallel GPU setups that were cured by switching to a serial config?

From where I sit, properly installed and implemented they both get the job done with equal efficacy.

yep if properly installed, dual gpu parallel and series will have indistinguishable temp differences. hence why suggest switching from one to the other?

I have measured it myself with calibrated thermocouples, as has other testers. What really ends up happening is... dual gpu in series has gpu temps of 45 and 46, and parallel has gpu temps of 45.5 and 45.5, though never see that until correct for water block contact and load differences since those exceed miniscule water temp differences between serial/parallel. And mathematically it isnt possible for them to be more than a degree difference with dual gpu/cpu unless one or the other is done poorly. Over 10 years I have seen many post about uneven flow problems with parallel loops (done incorrectly), serial is simpler.

If he had setup parallel, I wouldnt tell him to change to series. And I definitely wouldnt tell someone to change from series to parallel, less simple and no real difference.

Here is koolances description of their blocks series vs parallel:

The configuration you use depends on your individual cooling system. A common misconception is that running parallel paths in the same loop is always better. Experimentation is usually suggested. Keep in mind that parallel lines reduce coolant pressure, so results will depend upon the pump and tubing configuration. In a serial system, only 2-3°C is typically added between video blocks.

To illustrate this point, let's say two video blocks are connected in series. The first video block is operating at 45°C, while the second is at 47°C. This is disturbing to some users. They want both video blocks at exactly the same temperature, so the blocks are reconnected in parallel. However, due to the pressure decrease of parallel paths and additional restrictions in the loop, both cards may now operate at 48°C.

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Hey guys I'm back from the dead.

EVGA backplate is on the way and out of nowhere a discussion about parallel and serial. I could do parallel...it'll just involved ANOTHER shipment of fittings. But I could, and it'll make my loop better, I think.

From my current standpoint, the GPU goes to CPU. If I do parallel, the tubing will go out the left side and will be almost a straight run to top rad. Then an odd run to the CPU then another odd run from CPU to the res.

I'd do it but, I honestly don't care that much about equal temps. I'll save it for a second WC build when I start from scratch.

My current plan is to KEEP serial and to remove the overheating GPU, take of the block, check to see if there was contact with TIM, flush it out, maybe daring enough to open up the block and see from there, reseat it RIGHT this time, screw on the EVGA backplate, reseat it back, make the tubing run from GPU to CPU longer so WC vets don't get angry, and refill the loop and go through the whole priming again. What FUN!

Curious question, whenever I do a gaming session for a while or have the computer running for a long time, bubbles start to rise in the res.

Is it a concern to temps or anything? Fans are halfway on FC, needle pointing straight up on fan controller. Temps gradually rise during gaming sessions as well from start to end about 3-5 C but I assume that's normal.

rge said:

yep if properly installed, dual gpu parallel and series will have indistinguishable temp differences. hence why suggest switching from one to the other?

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It wasn't me who made the suggestion. As I said I don't think it matters either way. Pick one and run with it. As long as you have enough radiator area, coolant flow, and air flow either will do just fine. In my opinion which one you choose is far less important than how you implement it.

I have measured it myself with calibrated thermocouples, as has other testers. What really ends up happening is... dual gpu in series has gpu temps of 45 and 46, and parallel has gpu temps of 45.5 and 45.5, though never see that until correct for water block contact and load differences since those exceed miniscule water temp differences between serial/parallel. And mathematically it isnt possible for them to be more than a degree difference with dual gpu/cpu unless one or the other is done poorly. Over 10 years I have seen many post about uneven flow problems with parallel loops (done incorrectly), serial is simpler.

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I simply don't feel that strongly about it either way and I couldn't care less over a degree or two difference. Someone who would tear their rig apart chasing that difference probably has too much time on their hands...but to each his own. As for the people who had problems with their parallel set up, I will only say that some of the issues might have been the result of an error during installation that could have just as easily happened if they were running a serial configuration (like improper installation of a GPU block). Again, it isn't important enough for me to spend time digging up old threads about it. So we should just agree to disagree on the risk/complexity of a parallel configuration.

ok, next time i'll elaborate more
since we're troubleshooting, a (partial) breakdown of the loop is inevitable.
Thus, this is also a time to consider alternative routing... for performance; for ease of use: drain/fill; heck, even for "looks"...
I am not a big fan of parallel myself, but it IS an option to consider

Ok all, backplate is in my arms and is ready to get installed.

Anything else I should double check while I'm going to install and where should I drain? Should i get the fill port at top, tilt over case and empty water into a bowl?

To reassure everyone I have my steps:

1. Drain the loop.
2. Remove the tubing off of the top and bottom GPU.
3. Remove both cards.
4. Take off the Bottom GPU water block, flush it with distilled, if by your recommended instructions, screw the block apart to check to see if anything is interfering with the cooling.
6. Slap it back on with new EVGA backplate.
7. Re-install both cards
8. Replace the CPU to GPU tubing with longer tubing.
9. Have fun with the filling and priming process.
10. Hope you guys knew I was being obviously sarcastic with 9.
11. Turn on the computer and hope for the best.
12. Cry if this method fails.

I probably forgot a few in-between steps, hopefully nothing crucial, if so please tell. If you guys have any more recommendations, please tell.

RnRollie, yeah, but that requires buying more tubing and more $10+ fittings. Not now that is, when I break down the loop and possibly upgrade, that's when I'll actually change something. That time isn't now, maybe it'll be in the upcoming summer or next winter.

On that subject, I plan to try parallel, and a bunch of other things. Now I don't have so much time anymore, so you could only guess spending so much time on this would be stressful.

Eugenius88 said:

Ok all, backplate is in my arms and is ready to get installed.

Anything else I should double check while I'm going to install and where should I drain? Should i get the fill port at top, tilt over case and empty water into a bowl?

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That's my basic method...just be careful that everything is unplugged and don't get water on anything, it's a largely common sense thing once you get it started.

Well I've been gone for almost two years and I feel the need it's time for an update.

Sadly enough, the backplate was never installed, I realized draining the loop would be a plethora of work, so I settled with my single gpu setup. I have tried disabling the GPU with, I'd presume be the faulty backplate, but I still am not sure to this day, and attempting to get the top GPU working on its own but that rendered numerous BSOD. Not sure why and I still settled with my single GPU.

Why am I here today? Well in the two years I've been gone. I haven't touched my loop at all, besides cleaning dust as of recently, excluding my push config bottom radiator. Not cleaning that made me start to have a lingering thought. Maybe I want to upgrade soon so I'll hold off cleaning that and that would be removing a fan one by one, dusting and reinstalling, so on and so on. I thought I might as well clean when I upgrade. Not much else happened from there and I finished cleaning my system and decided to play some video games.

As of recently, I've been playing League of Legends, Rocket League and World of Warcraft all on high/ultra settings and it's been great. However, just today I bought Black Ops 3 and Fallout 4 and nearly the worst thing happened to me. Both games auto detected my video settings to low. Now that's when I came here, looking for help.

Mobo, Ram, CPU, and GPU. Standard upgrade. And a GPU block. Good to go!

Nice to see you again Conundrum Well now I'll have to plan it better than I did before :/ My 16 year old self wasn't the smartest person so hopefully now I can be more prepared and start to think ahead. I'll decide on the parts soon and then I'll revisit and layout my plan.

Skylake 6700k?

I am in a similar boat as u Eugenius. I not touched my loop in 2 1/2 years other then to add a bit of fluid. When i decided to
rebuild in a new case i went with the skylake cpu ,980gtx and a 950 ssd nvme m2. Hardest part for me was getting the wb i wanted
for the gpu. Man that was a pain.

Btw reading thru your thread i just add i had a similar experience with high temps. It turned out the wb had been mis milled and
it caused me tons of issues before i finally got it sorted. I swore off EK wb after that. It was my first attempt at water cooling.

Good luck with your next build !!

So the fact of me being lazy still holds to this day, I realized I don't need to deconstruct my loop yet and spend a bit on upgrades. I have decided I'm going to buy a 1070 and disable all PCI slots for my 590s and just let the water cool my CPU and have my 1070 go air cooled. It's the lazy man's way

Once I save up some more money from my job, which I got after my most recent post, I'll be planning to downsizing my build since 1070 series won't need massive rads to cool them down, once I figure out that build and save enough money up, I'll be starting a new thread and going from there.

Also, I've learned a lot from this build, which is plan accordingly and BUY QUICK DISCONNECTS FOR THE LOVE OF GOD BUY QUICK DISCONNECTS!!! I don't want to run into the same problem I did now, because this laziness would have easily been avoided if I had bought and applied quick disconnects to my build. Well, going from the age of 16 to soon to be 19, I've learned quite of bit of life skills so I ultimately plan to make a more badass, downsized build, definitely with a Corsair 540, 1070, Skylake.

With that information and my posting tendencies, I'll see you guys in a good amount of months

Eugenius88 said:

Well, going from the age of 16 to soon to be 19, I've learned quite of bit of life skills

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I would have never thought laziness would be one of them.