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Flash's Cooling Project - Page 3

Ok, time for the excuses. It's messy, I'm a messy person...

This is working, cooling the white PC (server) with a cpu temp of around 28c (37c under full load using 'stress -c 10')

I'll try and explain what's going on here with more pics. The black plastic tub at the top is the reservoir - it allows me to fill the system, it gives somewhere for the air bubbles to escape. It also allows any thermal expansion if the water gets warmer. Without this expansion the pressure in the pipework would increase when the water got hotter and put more pressure on the joints, leading to leaks. (Interesting point - if you pressurise a water system you can increase the boiling temperature well above 100'c - good for car radiators, but if it gets that high in this system, something went badly wrong...)

Dog toy far left...

Rad on left. Note clip-on thermometer on the return at the bottom. Not very accurate, alas. To get real water temps you need sensors in the water path.

The copper going back up was initially the feed to the header tank. However, some air bubbles were getting trapped in the return, so I've taken a swept T in 15mm plastic (just to the right of the copper) up to the header tank. This catches the air bubbles which vent in the tank. The white pipe in the middle is the return to the radiator.

The water leaves the rad at the front here and takes the white 15mm plastic pipe along the back. On the far-right you can see it go 90' upwards to the pump.

That wall is filthy! Because of the dogs shedding mud elsewhere in the house, the computers running 24/7 would suck phenomenal amounts of dust through this area coating everything in filth. Motherboards, walls, desks.

Anyway. Central heating pump mounted vertically and pumping upwards - this helps vent air bubbles which otherwise get trapped in the pump and make it noisy. The pipes in front of it are the return from the computers. At the T, the upper vents airbubbles to the reservoir while the lower feeds the rad.

After the pump, the water comes into the backmost of these two contraptions. The return comes out from the frontmost and heads off left to the rad.

Once this was on with the CPU block plumbed in, I filled with water, watched for leaks and didn't see any. I ran the entire system on speed III for 24 hours to test at a higher pressure and still no leaks - time to get the server down from the loft!

The day's running also eliminated all the occasional gurgling noises as the air gradually separated from the water. The only noise now is a low "thrum" just on the edge of hearing from the pump.

Installing the first computer

You see - putting servers in lofts is not always a great idea. This spider was happily catching flies that were crawling into the case for warmth through the missing blackplate!

This server records cctv via zoneminder, runs mythtv with two pci DVB-S tuners and a couple of extra usb DVB-T dongles. It's also a dev platform for coding work and hosts a bunch of samba shares, including the main one for the Popcorn Hour in the lounge.

Running an AMD 4600 twin-core, 2tb of disks (for cctv and tv recording)

Ironically, this HS/Fan combination (Hiper variable 80mm fan on a stock HS) is one of the quietest ones I have, but still very loud - it has to go!

Yes, that PSU does have "May be faulty?" scribbled on it. Pulled from a flaky machine, it turned out to be a bad motherboard, so PSU re-used in this.

The old Thermaltake block resting in place. A smear of thermal compound. Unfortunately none of the clamps from the old Thermaltake system fitted the AM2 socket.

Those 10mm-8mm joints are deliberately kept outside of the case - still not entirely happy about those!

I took the crossbar clamp off the old Heatsink/Fan and used that to hold the block in place - perfect fit!

I tried to touch the corner of the Northbridge heatsink too as that's now the hottest item in the box, but I don't think it makes much difference.

The water's going a bit rusty from the steel rad after a few days, not a problem but if it gets much worse I'm going to need some filtering of some kind. I'm hoping it'll stabilise as the oxygen works its way out of the water. The colour is mostly from residue on the inside of the pipe - the water's nowhere near that mucky, if you squeeze the pipe it disperses the residue.

Time to spin it up!

The PSU fan was now the only fan in the box, but with the desktop next door I couldn't really tell how noiseless this is.

Server started normally, straight into BIOS to watch the thermal values. All very cool as you'd expect - the CPU's not doing any work yet.

Can't avoid it any more - boot into Debian.

"watch sensors" allows me to monitor temps in realtime. All seems okay so I let it do its thing for an hour and a half.

Machine was running around 1.0 load, mostly CPU (Zoneminder is heavy on cpu because of the motion detection).

Ambient temp in room is 20'c. Cpu temp is 23-28'c - better than expected! (One core is always 5c below the other, no idea why that is)

The radiator temp was only about 2'c above room temp, not enough to feel a difference.

One week on...

No changes, system very stable.

I've tested with the linux tool 'stress -c 10' which hammers the cpu with 100% load. Immediately the cpu temps rise by 10'c - and stay there. Happy with that, when it was around 50'c idle with air cooling.

If I turn off the pump, the temp slowly rises as you'd expect. I bottled out at 50'c after about 90 seconds and turned the pump back on, and the temp immediately dropped again. Theoretically, you could use convected water instead of a pump but you'd need to do some serious calcs on pipe bore and head.

So far I'm very happy. With the low temps it really does open up the possibility of overclocking but mainly I want to get the desktop plumbed up too, so scouring ebay for cheap blocks...

Oh, and I de-cased the server. Neater, less space, more surrounding air, easier to work on. Note I've stuck a blue HeatSink onto the existing Northbridge HS with thermal adhesive. That's also getting warm so I know it's working. Turns out the PCI cards didn't need so much support, they're pretty good like that. Oh, and the hard drives. The old case was also acting as a sounding board causing a large amount of noise on seeking. Now they're suspended like this on corded elastic, the seek noise is only just detectable.


Now added my second PC to the other loop, CPU and GPU.

The GPU waterblock cost £10 off ebay and the CPU block was £5.

Temps on this machine in this location, uncased and not under load.

CPU: Before 39c. After, 27c.
GPU: Before 53c. After, 39c.


Another pic showing the cpu and gpu blocks being tested for leaks before fitting them;

The Australia-shaped gpu cooler is a "modified" unit whose seals had failed and sombody has re-done with silicone. I inspected thoroughly and tested to 3 bar and they're both good. Although half acrylic (ick), the gpu block contains a large amount of copper and the thermal mass is significant. And although intended for an Nvidia 8800 fits my PNY 9600 GT perfectly, same mounting points and covers both core and memory fine.

I do have a couple of chipset blocks too now, but waiting to see if they're neccessary. The desktop's northbridge runs at around 85c.

My room is again quiet. The only thing I can hear with the cupboard door closed is a very faint hum of the central heating pump. If you wanted to go further, you could place this a long way away - after all, these pumps are designed to push water around an entire house.

One month on...

After a month of both computers running 24/7, I closed them down to inspect the water, as the transparent pipes were pretty coated on the insides with rust. On draining some of the water though, it was totally clear. There was the odd bit of soft floating material (fungal or dust clumps?) but these wouldn't affect anything so I returned the water to the system with some anti-freeze to kill any life in there. (Bad idea introducing fresh water with oxygen to a closed system - it sparks off a new bout of oxidation). Obviously the rust is coating internal components, but very slowly and not remaining suspended. The running temps are all lower than projected and I've overclocked the GPU by 40% and it's still running at < 30'c in a room of ambient 20'c. Overall, I class this a total success!

This is a diagram of the final working system. (Click for bigger)

Future plans...

Case fans: I am considering de-casing one or both of these machines. They're in a cupboard, relatively safe and if I do it'll improve ventilation significantly. The only problem in decasing a computer that I can see is supporting the PCI cards securely enough. I might need to dig out some old cases and hack them up, or do something creative with metal and wood. Update: Both machines are decased and running free. Although not as secure as I like, the gpu even with massive cooler and two monitor leads feeding off it is still pretty solid.

PSU Fans: Can't realistically see water cooling working here (although I know it's been done). There are fanless PSU's but they're still very expensive, and I know that stopping a fan without adding cooling to a PSU will melt it pronto. I think PSU fans will have to stay, but worth paying a little extra for properly quiet PSU's. This may be the big compromise. (Update: Possibly decasing that and increasing the heatsinks may work, but that means exposed mains electrical parts inside my cupboard and I'm not a big fan of that.
Update: I removed the server's PSU fan as that was the loudest thing in the cupboard after the desktop was plumbed in. I replaced that with the Hiper fan from that server's CPU, declocked to 5 volts. Absolutely silent now.

Chipset Cooling: Ambient cooling, perhaps with additional heatsinks where needed but I deliberately choose motherboards without chipset fans as they are always failing and very loud, and with watercooling the case temps are also reduced, so these should be better off just by taking the cpu heat out of the case instead of just churning it around.


I don't recommend you do what I've done, not because it's difficult - it's well within anyone halfway handy - it's just that if it goes wrong it you'll have rusty water everywhere and your hardware may be damaged. But if you do decide to do it or something like it, this might help a little.

Precautions; Move as much electrical away from underneath, set safety cutouts in bios or software to throttle or shutdown your CPU if it gets too hot (if the water stops for example). Have buckets and mops handy for that first test...


Heavily inspired by the guy in America who used his swimming pool as a way of cooling his servers. Sadly his original page appears to be gone, but here's a taste.

Since writing this, I've found Vonslatt who's done something similar and he's even avoided a pump altogether!

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Flash's Cooling Project - Page 3