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Guide: Water Cooling: The Basics

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Aug 25, 2004
If you just want to know what to buy, scroll to the very bottom of this guide.

All prices are listed in USD.

Water Cooling: The Basics

Water cooling is the use of water to cool your processor. It is basically an expensive, efficient and (not always) quiet way to cool your computer.

How Water Cooling Works:
Basically, you have a water block on the CPU that absorbs heat, and passes it onto the water. Most water blocks are designed in such a way that a lot of heat is transferred to the water, with the use of mazes, that channel the water around, fins to increase turbulence and surface area, or, more recently, jet impingement. To move water through this water block we use a pump. A pump uses an electric motor to spin an impeller that forces the water through the tubing, and into the water block. To remove the heat from the water, we make use of a radiator. With a radiator, however, the natural convection of the heat isn’t enough for most users, so we connect a fan. 120 mm fans can be used, and these cut down on noise, while boosting airflow as compared to smaller fans. Because a fan has a dead spot in the centre and does not cover the whole of most radiators, a shroud should be used. After the radiator, the water gets pumped back through the CPU waterblock and the cycle repeats.

Water Blocks:

This is a chunk of metal that goes on top of your CPU. Its only purpose is to transfer heat from the CPU, to the water, and is probably the most important part of the system. If you want to upgrade, this is the thing to change. They are designed to get optimal heat transfer, and move the heat from the CPU to the water in the most effective way possible. Older style blocks used mazing, or routing the water, so it spends more time in the block and has more surface area, or pins, which increase turbulence and heat transfer area as well. However, mazes were pushed to the lower end with the release of the White Water, which utilizes jet impingement and mini fins. Jet impingement is the use of a conduit of water that is decreased in size, a restriction, to accelerate the water to fairly high speeds, so the water hits the base at a fairly high speed, reducing the boundary layer (a microscopic gap between the copper and the water, caused by imperfect copper and the surface tension of water) and carries the heat away quite effectively. Mini fins are tiny fins in the base of the block made to increase both turbulence and surface area.

The very best water block that is available is the MCW 6002. It may look bland, but it offers the best performance and one of the best prices ($40). In the UK or Europe the TDX is probably the best that is available now, as it is easy to use and fairly good. The RBX is similar but is harder to mount and use so any performance gains are essentially lost. The WW is slightly better than both the TDX and RBX but once again, has three barbs. This block is a viable option in the UK and Europe, as well as the RBX, due to a lack of availability of the 6000 series. There are many other blocks that offer comparable performance, but with the low price, high performance, and ease of use of these blocks, the others are probably not worth taking a look at.

If your water block has 3 barbs, the water goes in the middle, and out the sides, and these come with a Y fitting, that you use to reconnect those barbs.

When looking for water block ratings, lower C/W is better, along with a lower pressure drop.

Chipset Water blocks:
These are, as the name implies, blocks for your chipset. I don't suggest these, due to a restriction in flow, and no increased overclock, but if you are dead set on one, I suggest the DD Maze 4, as it has a very low pressure drop and good enough performance.

GPU block:
This is a block for your video card. Unlike the chipset block, this one does matter, although still not as much as the CPU block. The GPU block I recommend above all is the Silverprop Fusion block. These are built much the same as Silverprop’s CPU block, but made for the video card. The HL has higher barbs than the SL to avoid hitting RAM sinks. That’s the only difference. These are top quality blocks. The Swiftech MCW50 and the DD Maze 4 are both fairly competent as well, but there is a lack of reliable testing of the three so I have to make this advice based only upon what can be observed of the other blocks in the series (CPU and NB).

These move your water through your tubing. I’m not sure about the specifics of the inner workings of these, but it involves a spinning magnet and an impeller, which actually moves the water. Pumps have three ratings:
Flow: measured at 0’ head resistance, due to this it has very little bearing on the performance of the pump, but the higher the better anyway.
Head pressure; measured in feet H2O or metres H2O. This is the most important number, as we have got a lot of resistance in our systems. The higher the pressure, the better it is.
Heat: this is the amount of energy the pump draws, and it transfers most (50-75%, depending on the pump) of the drawn energy to the water.

I think I’ll make this fairly accurate generalization right now. ALL standard pumps perform about the same. By standard, I mean pretty much all pumps with flow between 180GPH and 5 feet pressure to ~400GPH and 12 feet pressure. In a typical system, consisting of a Procore and an MCW 6002, there will be NO measurable difference between these pumps. Changes start getting noticeable on the low end faster. The differences get larger with more blocks, and more resistance, but they’re still very small.

With that being said, I consider the Mag 3 to be the best pump out there. It has the best flow, but that is balanced by its high heat. It has a three year warranty, it’s relatively quiet, and it’s only 40 dollars. Use an unrestricted inlet, preferably 5/8” ID or higher. It doesn’t come with barbs, but you can get them free from the sticky in this section. The Mag 3 has minor problems with leaks, but these are correctable with Teflon tape or some sealant, such as epoxy, silicone, or JB Weld.

The Iwakis are the cream of the pump crop. The MD20RLZT provides the most pressure of any pump that is commonly used, with a fair amount of flow at all of the levels. It has slightly higher head than any pump listed here. It is quiet, and, like all Iwakis, is high quality, and incredibly expensive. It is highly suggested if you don’t mind paying a lot for a small gain, but be warned, it is large and probably won’t fit in your case.

The Danger Den DD-D4 (new revision out, quieter and weaker than old one) or MCP 650 pump (they're the same) is a high performance pump, with flow equalling that of the Mag 3, but with about ½ the heat. It is 12VDC, and sucks up to 1.5 amps. Form your own opinion about that. This pump is now fairly quiet, and has a life span of 50,000 hours mean time before failure, the best in the industry, and costs 75 dollars at the moment.

The Eheim 1250 is a very high quality pump, albeit with worse performance (once again, it doesn’t matter) than the other options. It runs at about 60 dollars, and is quiet. I suggest this pump for longevity, or in a situation that any minor failure is catastrophic. I have never heard of ANY problem with this pump.

The Hydor L30 is small, outperforms the Eheim 1250 (once again, does not matter because the difference between the two is so small) and is fairly quiet. A few problems have been reported with this pump, but they've been minor. It sells for around 50 dollars.

The Via Aqua 1300 is the cheapest pump out there. It is high heat, noisy, and low quality. The only reason I would advise this pump is if price is a serious issue.

Radiators are used to dissipate heat. A radiator usually consists of a large amount of very small, flat tubes, with fins attached to increase heat dissipation. There are used in cars, for the main radiator, and the heater core. The heater core is used to heat the interior of the vehicle while the main radiator is used to cool the engine. This is the best kind of radiator (I, and many others, refer to this kind of radiator as a heater core style radiator), but there are two others. The main alternative radiator type is the winding tube radiator. It involves a winding tube, with fins attached to increase heat dissipation. These are generally used in phase change coolers, where the objective is to get the liquid as cool as possible, rather than getting as much liquid as possible fairly cool, and aren’t very good for our purposes. They restrict flow a lot, and are usually more expensive than heater cores, and don’t dissipate the heat as effectively. The stacked plate radiator is built very similar to the heater core style radiator, but uses wide, flat tubes as the primary heat dissipation things, sometimes with fins between them, rather than using the fins as the main way to dissipate the heat. It seems that these would as good as heater cores at cooling, but due to availability and price concerns, these aren’t used.

The heater core from an ’86 Chevette is a common choice due to its low price and small size. It has very good performance, low pressure drop, and a damned good price (Around 20 dollars in an auto parts store.) It does, though, have one 5/8” barb, and one ¾” barb, so you have to change them out, or stretch your tubing over it. The ¾” one will be tough to stretch your tubing over. You can buy a shroud already made from Dtek for this radiator. If you don’t want to mod the radiator yourself, you can just buy a Danger Den heater core for 12 dollars more. This is about 7X6”, so it won’t perfectly fit where a 120 mm fan would fit. Dtek now has a radiator out that is about 7"*5" which would be a better fit in most cases. A better choice than either of those, though, would be a single pass heater core from a ’76 Chevy truck without air conditioning, but it is much larger (12”X6”) and slightly more expensive. Also, you cannot buy a shroud for it already made. This has a list of all the heater cores, one arranged by length, and one by width. For the car references, one is arranged by core number, and the other by model name.

Now, there are also the made-for-PC options. The Black Ice Extreme is the most commonly used of these. It fits where a 120mm fan fits, and fits a 120mm fan without an aftermarket shroud (shrouds are still good.) Its performance is worse, by a fairly large margin, than the heater core (2-4C), but it costs a lot more, and restricts flow more. The BIX2 is just slightly worse than the heater core, and is much bigger. Black Ices also come in an 80mm size, and a 160X80mm size, but these are probably below your desired level of performance There are also the Thermochills. They come in a bunch of sizes: 80mm (80.1), 92mm (92.1), 120mm (120.1), 240X120mm (120.2), and 360X120mm (120.3). The 120.3 outperforms the standard heater core, but I doubt it outperforms the 10X6 single pass core. (There has been no good testing done, but assumptions can be made from other testing.)

Do NOT buy radiators smaller than 120X120. That is just high temperatures, wasted money, and a lot of frustration waiting to happen. Do NOT buy a winding tube radiator. Once again, a bad cooler, and really restrictive...

Modding a Heater Core to Fit your Tubing:
1. Take note of the pipes (input/output) coming out of your heater core. Generally, they will be roughly 1/2 inch copper. Sometimes they have bulbed fittings on one end, but at some point the pipes will be the same diameter. This is where I would cut them off at.

2. Get a hacksaw, and put your heater core in a vice. Just set the "tank" of it in there, and be careful not to crush any fins. You don't need to crank it in there, just snug. Slowly, and gently, saw off the pipes until they are both at the same diameter. Try to not bend the pipes, or crush their diameter. If you do, no problem. The pipes are pretty soft, and if you put something like a pair of dikes or pliers inside them, open them up, and move them in a circle, you can restore them to their original shape very easily. Don't worry about this too much, anything can be fixed with some solder and some sweating .

3. Grab your heatercore and go to a hardware store (Ace, Lowes, Home Depot). You're going to want to go to the plumbing department, and look for some barb fittings. One side will have a barb, and the other will be threaded. If you heater core had 1/2 inch piping, then you'll want to grab a male brass fitting with a threaded size of 1/2 inch. The barb size will be dependant of the inner diameter of the hosing that you will be using. The male piece should slip right over the fitting, but a female piece will work too, it will just require more solder. Bring your heatercore with you, just to make sure, and if you get confused, ask someone there to help you.

3. Now that you have you fittings and a sawed off heater core, it's time to do some soldering (sweating copper). If you don't have any flux, solder or a torch, you should pick one of these up at your hardware too. A small torch runs about $8, and the butane for it $2. You can also pick up a sweating kit for about $6, which will include some emory cloth, flux, solder and probably a brush. Get it, if you don't have anything else.

4. Sweating copper is pretty simple. First, make sure that the pipe on your heater core is free of any corosion. Use the emory cloth to clean it up a bit where you will be sweating. Next, take some water, or alcohol and clean off the shaving or dust from the sanding. Make sure it is DRY afterwards. Take you brush and brush some flux on the inside of the fitting and the outside of the pipe. Slide your fitting over the pipe, and spark up your torch . You're going to want to heat the piping and the fitting up for a couple minutes. Yes, you'll probably see some smoke this is okay. Run the torch around the pipe and fittings until they are nice and hot, and then take your solder and run it along the seam of the fitting and the pipe. The flux will draw the solder in and you will create a seal. You don't need a lot of solder to do this, unless you are using a female barb fitting. BE CAREFUL!, the pipe will GET HOT. I would advise using a vice for this also. Once your solder and make a seal let it cool for a few minutes, and then dunk it in some water.

5. Thats about it, you now have your fittings. Your next step is to leak check it. If you have all your other WC supplies, this is easy hook it up and let it go, monitor it for a couple hours. If you only have the heater core, you can attach some tubing to both ends, crimp one end closed place the heater core underwater, and blow into the other end. You're not putting a lot of pressure on it, but I doubt your WC really will eaither. If you have a compressor that would work great too, but I think you get the idea I'm going for. Look for bubbles. If you see one, get your solder and torch back out and go to work!

Thats modding a heater core in a nutshell. You can do all sorts of things to them, but I think this should give you an idea. I wish I could help you out more with the sizes, but a little research on NAPA.com or any other such site will get you there. All the dimensions are listed, so just compare them to what you are looking for in a fan.
Big thanks to bswitt for this basic modding guide.

Shrouds are used to attach the fan to the radiator, and to distance the fan from the radiator as well. You want one that spaces the fan at least 1” (1.12" being preferable) away, and, naturally, it should fit the core tightly. If you have a DD heater core or a heater core from an '86 Chevetter of the same size, this could be useful: http://www.overclockers.com/tips1138/ You can also buy 12 dollar shrouds from dangerden, but they offer no improvement in performance.

Fans use a DC motor in the middle of the fan, with blades on the outside to move air. You want 120mm fans, or larger, because they don’t have to rotate very quickly to move as much air. Basically, get the fan that moves the most air for your noise tolerance. 70CFM should be considered a minimum air movement speed, and below that performance suffers. If noise is a really big issue to you you may want to consider going well below that anyway.

Filling and Bleeding the System:
There are two main ways to fill/bleed your system, the reservoir, and the teeline. A reservoir is a large holding tank for water, and it usually has a place in which to put the water. The easiest way to fill and bleed the system, but it consumes space, and costs money. A T-line is essentially an upside-down T somewhere in your system. It is basically a small resevoir. This is cheap, and saves space. I advise a reservoir if you have the space.

If you don't want to submerge your pump, you can either use a PVC reservoir or a bay reservoir, which comes in multiple sizes and configurations. You want one with a divider in the middle so less air is sucked back into the system. Submerging your pump improves your flow, but there are no commercial options, so the best method is to put it in a small Tupperware container, and then fix it up so it can close.

This is what the water flows through. Larger ID is better, but ½” is standard, so it is easiest. You want thick walled tubing (1/8”, ¾” OD for ½” tubing) to avoid kinking.

Tygon is the preferred type of tubing, but it offers very little advantage for its cut throat price, of around $2.60 per foot. Clearflex 60 is next, very similar to Tygon, a little less flexible and stretchy, but it shouldn’t be a problem (all you need, in my opinion). Next in line is tubing from the Home Depot. Look at the tubing there, and make sure it isn’t squished, or pre-kinked. It is cheap, and easy to get, although it does not bend as well as the other two (steer clear of this stuff if you can). You can get good cheap ClearFlex 60 tubing from http://www.mcmaster.com. The tubing I personally like is product code 5233K68. Found out these guys don't ship to Canada anymore. Home Depot has some good braided tubing that isn't too expensive though.

Hose Clamps:
These are NOT optional. Put these on every barb, and prevent leaks long before they start. There are two kinds, these being, steel worm drive, and nylon hose clamps. Steel worm drive clamps are tightened with a screwdriver, are durable, and hold very well. The nylon hose clamps are put on with pliers, are plastic, and hold well enough. I advise buying steel worm drive clamps, available at Home Depot.

Cooling Fluid:
For best heat transfer/heat capacity, nothing beats pure water. However, there is probably a good chance that you have aluminum (even anodized needs it) or a possibility for biological growth, so you must add an additive. Swiftech HydrX is probably the best choice out there, although it is expensive, so antifreeze is a very good alternative. If you have no aluminum in your system, 10% is fine, but if you have some anodized aluminum ~25% is recommended.

Kits are bad news. If you can customize the kit, with good components, and it will be cheaper, go for it. The Flowmaster XT is the best example of this.

Reasons Not To Buy A Kit:
1. The best kit is worse than the best aircooling.
2. They are expensive for what you get. In fact, they're just plain expensive.
3. Very little upgradeability. If you decide you want to switch to a MCW 6000, or a better radiator, you will have to change everything else.
4. This is an extension of 3. They come with crappy parts. No part of the system is better than the parts you could get custom.
5. Some of them are rather loud.
6. They still require you to intall them.

What to buy:
For those of you too lazy to make your own decision, here's my advice that I would give you in a thread.

Via Aqua 1300 ($20) (You might as well go for the Mag 3, for 15 bucks more), TC-4 ($25), Heater core (~$20), Tupperware for shroud and reservoir, Home Depot tubing, 120mm fan (~$10), and hose clamps.

This may be above your budget, which most people put at around 100 dollars for a cheap watercooling, but, spending the extra 20 or 30 bucks now will be worth it.

Mag 3 ($40) or the DD D4 pump ($75), MCW 6002 ($43) heater core (~$20 [local auto parts shop]) or DD heater core ($30) shroud ($1 or $12), Clearflex 60 (10 ft.), 120mm fan (~$10 [your choice]), and hose clamps.

These are just general guidelines, some of you may like to cheap out on tubing, but go crazy on the pump, or do some such thing.

That's pretty much all there is to it. If I made any errors, or omissions, do not be afraid to let me know.

If you want to get a more advanced understanding of water cooling, check this site: http://thermal-management-testing.com/ and read BillA’s comments about testing, and water cooling in general. Very informative.

Credit for this guide (except for minor alterations by myself) goes to AngryAlpaca of the Extreme Overclocking Forums.
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I would Recamend Swifttech kits, they are of good quality and comes with a verry well don printed Manual, again though no kit (just like no store bought Computer) will ever out perform a custom engineered set up. How ever they are a great start if you get the right one !
XeonStrikeForce said:
I would Recamend Swifttech kits, they are of good quality and comes with a verry well don printed Manual, again though no kit (just like no store bought Computer) will ever out perform a custom engineered set up. How ever they are a great start if you get the right one !

I second that. While using the a swifty kit I switched out the rad(the really only bad part of the kit) with Black Ice 2. I only got 3 degrees better on idle and 5 degrees better on load(Prime 95 for 4 hours). I used the same fans with each.
good read, thanks for that. i had a guy suggest to me to use winshield wiper fluid, winter grade (that has alcohol in it). is this a good suggestion? also, can i get better performance out of something else such as anti-freeze?
Kamel said:
good read, thanks for that. i had a guy suggest to me to use winshield wiper fluid, winter grade (that has alcohol in it). is this a good suggestion? also, can i get better performance out of something else such as anti-freeze?

I haven't tested this myself but generally, using a small amount of antifreeze (5-10%) is good enough to discourage bacteria growth and give a good balance between performance and cleanliness.

I just use antifreeze myself.
Kamel said:
good read, thanks for that. i had a guy suggest to me to use winshield wiper fluid, winter grade (that has alcohol in it). is this a good suggestion? also, can i get better performance out of something else such as anti-freeze?

I know this is old but.. you do realize that anti-freeze does not conduct heat very well right? It is only used in cars to raise the boiling point of the water and to lower the freezing temp. Just thought i would throw that out there.
Bonddabomb said:
I know this is old but.. you do realize that anti-freeze does not conduct heat very well right? It is only used in cars to raise the boiling point of the water and to lower the freezing temp. Just thought i would throw that out there.

the antifreeze is used to prevent some algae growth and corrosion. that is why people use 90% distilled water wil 10% antifreeze
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do not use antifreeze it doesn't work to discourage bacteria growth just use some dealgaer for a pet supplies store like 2-4tablespoons works fine to prevent algae
Great info!

I'm a noob to WC but intertested. Question - What kind of up-keep/maintenance is required when running a watercooling set-up? Thx
You have to change your coolant at regular intervals (from 6-18 months depending on configuration/coolant) and keep your rad free of dust.
Why on earth do you have teflon tape wrapped around a barb? Teflon tape is not always the answer in watercooling.