Watercooling Guide

[Sin22]

Watercooling Guide

Introduction to Watercooling

Watercooling (a.k.a w/cing) has been around for a good many years. To my memory, for about 7~8years already and more likely longer than that. The benefits of using water to cool your CPU and other devices would seem as though it is a no-brainer to anybody.

But we have to set some things straight first. W/cing is not like aircooling whereby its only one component slapped on the CPU and off you go. You will always have to think of w/cing as a whole w/ced system. Its a combination of parts that requires each part to be mixed & matched with the most appropriate secondary & subsequent parts. To get the best performance out of a system, you have to optimise each part individually and then on the whole. Sometimes this does not happen and the result is a system which performs worse than some of the high-end aircooled heatsinks.

Explanation of parts

There are three main components of a watercooling system. There are several other secondary parts that can be added or switched out for which I will explain as well, but the three main parts will be as follows:</p>

Waterblock

The most important component, without this, there is no point in watercooling. This sits directly on your CPU. It works by transfering the heat from your CPU into the base of the waterblock which generally are made of copper and then into water by ways of a specially designed baseplate. Each waterblock has a different baseplate design. The main importance of any design is to "ensure the greatest amount of water impacting with the hottest areas of copper with the most violence" [paraphrasing a statement made by Cathar]

To choose the right waterblock for yourself and your system, look at only two places for reviews. Overclockers.com Waterblock performance rankings and Procooling Watercooling Gear Reviews. These are the only two websites whose testbeds are in any way respectable and whose results can be trusted to a larger degree than the other websites.

The most important features to look out for are C/W ratings and Pressure Drop figures. Why ? Well the first figure tells you how well the waterblock transfers heat away from the heatsource i.e. the CPU. The lower the figure the better. It stands for the rise above ambient temperatures per watt of heat energy. So the lower the figure, the cooler your CPU will be. The second figure is more system specific as it shows how flow restrictive your waterblock is. The lower the figure the better once more since if say you pair up a very restrictive waterblock with a pump which does not supply enough pressure to the system, you would be severely curtailing the performance of the waterblock since the flow rate is greatly dimished in the whole system.

Pump
The next component is obviously the pump. There are a wide selection of pumps out there in the marketplace. The majority of pumps used for watercooling purposes tend to be aquarium pumps since these fit the specifications quite well.

There are two main types of pumps that you can use. Submersible or Inline. Submersible as the name suggests is a pump that needs to be fully submerged in a body of water before it can be used. An inline pump is one that can be left high and dry and just have the water moving through its impeller chamber. Inline pumps tend to be a lot more expensive than submersible ones due to the added costs of sealing the chamber from leaks.

However there are only two main issues that you ought to look out for when purchasing the pump. The more important issue is rated head. most pumps will come with a diagram or specification showing the amount of head delivered at 0 flowrate and another specification showing the amount of flowrate at 0 head. Head delivered basically is the measurement of how much pressure there is in the system, how high the jet of water can reach before coming back to earth. Look for a pump that delivers <em>at least</em> 2m of head. In a typical watercooling system, the max you ought to get would be one that delivers 4m of head as from that point onwards, there is a bit of a tradeoff between the amount of heat that gets dumped into the water from the pumps motor and the added performance of so much pressure in the system. As to flow rate, most pumps with high values of head would have a flowrate of 1200litres/hour which is sufficient.

What we are looking for is more crucially the flow rate of the whole system with all the flow restrictive devices connected. A) Waterblock, B) Radiator/Heatercore, C)Pump, D)Tubing etc etc. We are aiming for at least 4litres/min in the whole system. Checking most C/W vs. Flow rate graphs will show that this is the optimum point for most waterblocks where the greatest performance with the least amount of "effort"occurs. So to obtain that, we normally look for a pump with high head values.

Radiator/Heatercore

On the left we have a heatercore. On the right w have a radiator. The easiest way to distinguish them apart is the tops of the units. A radiator will have a lot of u-turn bends for each channel of water. The heatercore will be bare with header tanks on either end. Generally, heatercores are flat and long, with radaitors taking on more of a cube form.

Always get a heatercore if you can. These tend to have better flow characteristics through them. They have less flow resistance and as such perform better in your watercooling loop than a radiator since they do not impede the flow so much. If you did any Fluid Dynamics before, you will remember that each 90degree bend creates a large drop in pressure. Now calculate how many 90degree bends you have in a radiator and you get the idea of how large a flow resistance it can cause.

The downside of heatercores is that they arnt cheap. Commercial heatercores from watercooling companies range from the SGD$80 to SGD$180 mark. You can get heatercores from scrap yards from old cars or motorcycles but you do have to clean them up yourself and get someone to weld on the right sized bards for you.

The primary purpose of a heatercore is to remove heat from the water. Its acts just like a heatsink in the sense that all its tiny fins act to increase its surface area to the surrounding air. One downside of using a radiator or a heatercore is that you will never ever go below ambient temperatures. Dont ever kid yourself that your watercooling system is so good that your temp probes are reading below ambient temperatures. Its a physical impossibility since radiators/heatercore utilise ambient air to remove the heat from the system. The larger the heatercore, the more surface area, the better your temperatures will be. Dont forget to also include the increased flow resistance due to a larger heatercore but that normally balances itself out with the greater performance afforded by one.

Do not run your heatercore or radiator passively. i.e. Do not run it without any fans. Yes a watercooling system will be significantly quieter than a high-end heatsink with a Delta FFB0812SHE screamer on there, but if you start running it passively, the gains you obtain from no airflow just for silence is quite pointless. Get a good 120mm fan like a Delta AFB1212SHE and run it at 5v. At that speed the fan is near silent, and pushes sufficient air through the heatercore to allow for very good performance in itself. Increase the speed to 12v and you get a system that can withstand a lot of good overclocking efforts.

Placing of your fan is another crucial aspect. The age old question of sucking and blowing comes into play once more. Just remember that you will always need a shroud over your heatercore. And when constructing the shroud, follow these guidelines. If placing the fan in a sucking configuration, place the fan at least 3x the fan hub diammeter away from the surface of the heatercore. If in a blowing configuration, place the fan at least 5x the fan hub diammeter away, the further away, the better. This has got to do with the way the air comes out from the fan. Too close to the surface and you are overworking the fan and not really cooling a very large area on the heatercore. Further away, more air gets to go through the heatercore and you reduce the deadzone created by the central hub of the fan.

 

[Sin22]

Secondary Parts

Reservoir

A reservoir can come in many shapes and sizes. You can make one out of a shampoo bottle like above, or out of a tupperware or you can purchase a commercially made acrylic one. The main basis of one is to store water and to act as an airtrap for your system. The most important aspect of a reservoir is to keep the pressure drop across it as low as possible so that it doesnt act as another flow restrictive addition to your watercooling loop.

My personal views on reservoirs are quite neutral, they are useful for filling up your system and dont make the chore of priming and getting rid of the bubbles in a system very hard, but the downside is that its another item to try and squeeze into or out of the case. Use it if you want to, dont use it if you dont need to. Whichever you choose, you will need either a reservoir or a T-line in the loop so remember that.

However, if you chose a submersible pump, you wont need a T-line since your pump needs a body of water and that in itself becomes the reservoir.

T-line

This is a miniature reservoir in some sense. It consists of a valve with a T-section. This is where you add water into your system, where you top up water when you need to, where you attempt to remove air-bubbles that form in the lines. Its not as convenient as a reservoir but it does save a lot of space. Basically its an entry point into the closed loop of your system.

Tubing

There are two choices to tubing. Expensive and cheap. The expensive stuff costs around SGD$6 per foot for Tygon (Medical grade tubing) or SGD$4.50 per foot for Clearflex 60. The good thing about this tubing is that its easy to route inside a tight space as it does not kink very easily. The bad thing is that it costs a fair bit since you will need at least 6feet of tubing for a standard system plus some spare.

The cheap one is really cheap, going for as cheap as SGD$0.60 per foot but the downside is the kinking or toughness. It cant make tight turns and its generally very stiff so its harder to route.
One way to get around the kinking is to put a hoseclamp or zip tie on the kink (hose clamps work a lot better).

The main aim when using the tubing is to keep your tubing runs as short as possible. Optimise the placement of all the parts in your system so that when you connect everything up with the tubes, the distance between the two parts is as short as possible. The main reason for this is so that the tubes do not create even more flow resistance. The longer the tubes, the more wall friction is going to occur, the slower the main body of water will get.

 

[Sin22]

Alternative Cooling - Evaporative Cooling

On the previous page I talked about heatercores and radiators and how you would never experience below ambient temperatures on your CPU, also how the costs of these objects was quite high. Well there is an alternative to them and its evaporative cooling. With evaporative cooling your CPU still most likely wont go below ambient temperatures, however, your water temperatures will be below ambient temperatures and this can aide greatly in overclocking.

There are two main forms of evaporative cooling. The first is to use an evaporative tower a.k.a. a "Bong".

An evap tower basically is a long piece of pipe with a shower head on the top of it and a small inlet in the bottom where a fan blows into it. The water in the loop gets pumped to the top and into the shower head which sprays it out into smaller droplets. With the cold air coming in from the bottom due to the fan, the water then evaporates as it falls down the tower, cooling it down significantly. It then reaches the reservoir at the bottom and gets pumped back into the loop. The downside of this method is that there is still quite a fair bit of noise due to the dripping water. For more info do take a look at this article on Overclockers.com.

The second method is known as a swamp farm and this appears to be the best variation of it. It was made by Volenti of OCAU Forums.

Picture& concept property of Volenti​

Basically you have a large reservoir with these sticks coming out wrapped in towels. Water gets pumped to the top of the sticks and flows down them. The large surface area coupled with a fan blowing across the sticks promotes evaporation and you get cooler water once more. The downside of this is the sheer size of the reservoir and the usage of a secondary pump. More info can be found in this forum thread.

I recently used a variant of this design in the Abit O/cing competition and got the water temperature down to 10degC below ambient, around 19degC. I did it using active cooling supplied by 6 120mm Delta 1212SHE fans. Though it was noisy, it got the job done.

Each has its strong points and the main benefit of these forms of cooling is A) the cool very well B) they are cheap to make. The downside is that they are relatively large and in the case of the evaporative tower, can get a little noisy.

Review

In the previous pages I've gone over each of the possible components that can be used in a watercooled system and what ought to be looked out for and optimised, a quick overview of each components important aspects

Waterblock

• Low C/W rating coupled with low pressure drop or one which is acceptable to your pump
• Preferrable with only 2 barbs as easier to route tubing

Pump

• High Head, between 2 ~ 4m
• Submersible or inline depending on costs and personal constraints

Radiator/Heatercore

• Always choose a heatercore if possible
• Larger heatercores = more surface area = better cooling which offsets the increased flow resistance
• Min of 3x hub diammeter for sucking or 5x hub diammeter for shroud lengths for fans * this can vary depending on strength of fan

Reservoir + Tubing

• Personal decision as to which is more useful
• Keep tubing runs as short as possible

Alternative Cooling

• Cool very well, where water goes to sub-ambient temps and are relatively cheap
• Large in physical size

Overall

• Make sure all the metals in the loop are the same. i.e. Copper waterblock with copper radiator and so on. Do not get an aluminum radiator and a copper waterblock or else you will be getting galvanistic corrosion occuring. (I talk more about this in the FAQ in the following pages). Basically, dont mix metals ever if you can help it.

Setting UP
Once you've chosen the right parts for your computers , comes the setting up of the system.

Its broken down into three main steps:

• Place all the components inside your casing with all the hardware already installed (CPU, Mobo, HDD, PSU, etc) to get the approximate locations of where you want to place your watercooling loop components. Remember the golden rules of, A) Keep tubing runs as short as possible. B) Keep your radiator as close to the ground as you can feasibly do so as ambient air is cooler down low. Once you have the approximate locations, take your tubing and measure out the lengths and cut. (Measure twice, cut once!)
  
• Once that is done, take all your components out and attach each component together with the tubing. Remember to always always place either a hose clamp or a zip tie one each end. Any connection must be sealed tight. There are now two ways to fill up this closed loop. A) You can pour water into your reservoir/T-line and start your pump up, alternating between pouring and starting up your pump or B) place the pump into a large bucket and the one end of the outlet hose of the system into the other side and start the pump, once the whole system is clear of air bubbles (make sure you knock it and shake it abit to dislodge them), connect the outlet hose over the inlet barb of the pump underwater and you have a closed loop.
  (More info can be found in this article). Do remember to use Distilled Water at least. These can be had from most Petrol Kiosks for $1/litre. A normal system would utilise about 1.5L of distilled water. The main reason is that distilled water has the best thermal properties of any coolant for a watercooled system. The only time you add any additives to the system is to prevent galvanistic corrossion and algae growth. (For more info on coolants, please read these two excellant articles on O/cers.com. Coolants Part I & Part II).
  
• Leak testing is the next step. Run your system as it is now for at least an hour with a dry piece of paper underneath it to pick up any leaks. People normally suggest running it for 24hrs but I've yet to really do that. Just keep an eye on your computer parts and if you are worried do run the 24hr leak test.
  
  
  
• Now all that is left is to place everything back into the system and to make sure you do a good mount on your CPU. Its not like a HSF anymore, mounting a waterblock and getting the perfect mount takes time and practice. If your waterblock is bolted to your motherboard as it generally will be, try to not let your hoses have any torque force on the block when mounting. Also follow the mounting instructions of a criss-cross pattern of tightening the hold-down screws.Once its mounted, start up the pump and your system and verify that temperatures are ok and not sky-rocketing which would indicate a bad mount and you're off to a good start.

Along with all of this, Procooling has some good useful tips for watercoolers. Have a read of their article here and give the ones that you feel are beneficial to your situation a shot.

Conclusion

What I have just talked about is the most basic of things to know about watercooling. The whole topic of watercooling and the knowledge required to truly understand everything will take a lot more than what I can fill on just 4~5 pages and also is a lot more than what I currently know. But it all has to start somewhere.

Following the guide I've just done up in setting up your system and what to look out for and optimise in the system is the starting point. From there, you can go on to experiment with different configurations, different parts and waterblock designs should you decide to try your hand at it. But always remember, we watercool not only for the silence, but for the performance and the sheer thrill of overclocking and pushing our hardware as far as it can go. This is but a small step onto larger things. Peltiers & Phase Change systems still await and beckon

This guide was taken off my personal website and can be found here. There ought to be a couple of mistakes here and there that I've not corrected, but shouldnt be too big an issue. DO PM me though if you spot any. Feel free to ask questions as well in this forum/thread but I will periodically clean the thread up. All content/pictures are the sole property of ME, so please ask permission first before flogging this stuff off.

 

[Sin22]

FAQ

Q: What are the benefits of watercooling?
A: Silence and performance. With CPUs getting hotter with each generation, larger heatsinks with larger and more powerful fans are being used. With watercooling, you increase the cooling capability whilst decreasing the amount of noise generated by a 5,500RPM 60dBA fan. For overclockers, watercooling is the next step as with the increased cooling capabilities, they will be able to overclock significantly more than on aircooling. </p>

Q: How much would different setups cost?
A: I've been asked quite a few times how much it would cost all up for a watercooling rig.

Locally in Singapore , you can get Silverprop, Swiftech & DangerDen watercooling gear through their distributors.

Pumps
Pumps can be locally bought easily. An Ehiem 1250 is the de facto one for most people costing $100 from PetMart in Serangoon North. If that is too costly, an Ehiem 1048 will set u back about $75 I believe. If not, you can go looking for a decent aquarium pump but remember, head delivered is the key specification to look out for.

Waterblocks
Unless you are going to go and grab only Silverprop/DangerDen/Swiftech items, then you will be looking overseas to purchase your gear. There is a long list of online shops in this guide over @ CMF. For a cheap and decent waterblock, you could grab the DangerDen Maze4 which retails for SGD$80. For the best in the market at the moment, the DangerDen TDX retails for S$100~.

Radiator/Heatercore
This depends on your size of casing, how much cooling power you think u may need and your budget. Most radiators/heatercores can accomodate either 1x120mm fan or 2x 120mm fan. You have to decide which you may want. For the cheaper and better option. The DTek Pro Core combo rad (1x120mm) costs US$54.99. You could to save some cash on shipping get the Silverprop Silverstorm 4 or Thermochill 120.2 which costs in the S$150 (2x 120mm) region.

Tubing
Tubing and hose clamps can be obtained easily from most hardware shops really. Ehiem is generally used or just clear PVC tubing though it kinks quite easily. The Ehiem ones costs $1.20/ft I believe from most aquariums.

Tallying everything up.

Budget Rig:
Ehiem 1048 - S$75
DD Maze4 - S$80
DTek Pro Combo - US$54.99
Shipping - US$30
Total - ~S$280

Kickass Rig:
Ehiem 1250 - S$100
DD TDX- S$100~
Silverprop Silverstorm 4 - SS$150+$30
Total - S$380

Dont forget to budget about $20++ for the misc stuff.

Hopefully that gives you some idea as to how much it may cost and what to budget for. It can add up over time if you add NB & GPU blocks.

Q: How safe is it ?
A: Relatively safe. Honestly speaking, you have a higher chance of your pump failing and causing ur CPU to overheat than for a leak to spring and short everything out as long as you use hose clamps and zip ties on all connections. Furthermore, the coolant used is distilled & de-ionised water which means that it is electrically inert when purchased, though it does get ionised once inside your system. Should the unlikely event occur that you do spill it all over the insides. Dry out your stuff thoroughly and it ought to be perfectly fine the next day.

Q: Coolant ? Whats that?
A: Ok, never ever run tap water in your system. Though it is fit to drink, it is terrible for your gear. Tap water is full of gunk in it as well as ions. It will do a far amount of damage. Firstly galvanistic corrosion is further sped up due to the ions present in tap water. This occurs when two different metals are placed together and one metal in time will corrode the other. Very very bad in aluminium copper systems. The second thing about tap water is that it will generally result in algae growth a lot faster than normally expected. So, just pick up a bottle of distilled water or radiator water from an Auto shop. Whilst you are at it, grab a bottle of radiator coolant as well, that contains some anti-corrosive properties which will help in your system. More detailed info can be found in the above two mentioned articles.

Q: How should I place the fans? Blowing or sucking?
A: It depends, but the general consensus is to suck through the radiator. Why? Because look at it this way, when you are sucking air through the fan, it is pulling air in from all sides. However when you blow, the pressure difference is fairly large. i.e. a dead zone in the centre followed by a large pressure distribution diminishing as you go further out. However, if you have a large shroud that places your fans say 5+cm or more from the radiator surface, its seem better to blow as the dead zone is eliminated. If your shroud is just off the surface, it would be better to suck through. Test them both out and see whats best for you. As you could see from above, that config gave me a great drop in temps.

Q: Pumps and flowrates and head, whats that?
A: A pump is rated to deliver a set amount of flowrate/hr at a certain amount of head at its best settings. Head is defined as how much water and to what height its ejected to. The higher ur head is, the greater the pressure. This is extremely important in a system. You gotta realise that some waterblocks and radiators in particular are full of twists and bends and very restrictive to flow. The higher your head is, the higher the pressure, the greater the ability to push more coolant through the system and cool things down better. But also there is a trade off, the higher the rating of your pump, the more heat the pumpwill dump into the water. So things might heat up a bit as well unless you use a submerged pump instead of inline. Higher the flowrate, higher coolant flow, better temps.

Q: Northbridge, GPU cooling ?
A: Yes both can be watercooled. I've had a pair of Jaron Esky waterblocks just for that.

Generally though, the NorthBridge does not need such active cooling till getting past the 280MHz FSB mark for i865PE/i875P mark in my experience.Watercooling the graphics card is a better option as high-end graphics cards are getting hotter by the day and there will be a tangible overclocking difference when watercooling your GPU. Do remember, the more things you add to the loop, the more restrictive it gets and as such, you will see a slight deterioration in temps and perhaps performance.

This guide was taken off my personal website and can be found here. There ought to be a couple of mistakes here and there that I've not corrected, but shouldnt be too big an issue. DO PM me though if you spot any. Feel free to ask questions as well in this forum/thread but I will periodically clean the thread up. All content/pictures are the sole property of ME, so please ask permission first before flogging this stuff off.

Enjoy

 

[zero_cool_108xxx]

since you happen to give an advice, you might want to give advice where i can get some aluminum bar stock, i am a home machinist and i started creating my H2o block on CAD.need help asap

 

[Sin22]

You arnt planning on running an alu + copper hybrid loop now are you?

Anyhow, you can get alu, brass, copper bars from Kelantan Lane, its near Sim Lim Towers. Have a walk through there and you'll spot the shops quite easily, they have rows upon rows of metal bars displayed infront.

 

[jason6142004]

Question.......

I m buying a pump. But I hav not decided on wad pump... Wad pumps do u recomend which cost less dan SGD$75 as I hav limited funds....

 

[greenbubble]

How to fix the tube to the reservoir without leaking? Let say I'm using tupperware or plastic container.

 

[Sin22]

Use silicon sealant. Use an epoxy first to stick the barb to the plastic container, followed by silicon to seal it.

Best would be to find barbs that have a screw on end as well for an added safety feature.

 

[darkmatt]

Is a Liquid Nitrogen Cooling System practical?

 

[Sin22]

You asking seriously or you just trying to make fun of things?

Think it through.

Depending on your answer then I'll either respond seriously or delete the posts.

 

[darkmatt]

I'm asking seriously.... i read about it.... Just dunno if it's possible/practical

 

[Sin22]

Well it all depends on the system itself. You're talking about a sealed system that has to have a pump capable of working at -175°C and the seals as well to not dry out and crack. LN2 by its nature is liquid at those temps, but then depending on the amount of heat you start exposing to it, it will bubble and convert into a gaseous form, so basically, the sealed system must be capable of handling that too like a phase-change rig, and then how do you go about removing the latent heat as well? So you need another heatercore/condensor to get rid of the added heat and get the LN2 back into a liquid form. Overly simplified explanation really.

All up, possible, as you've probably seen/read, and has been used in certain occasions, but hardly practical for a computer system or most circumstances. However, an easier form is just using the tried and tested phasechange cycle. The coolant used is a lot more stable (R22a/R143a etc) and easier to work with. For greater temperatures, cascades are used like what Shamino and several others worldwide have built, which are basically phase-change systems cooling another cascaded phase-change system utilising a different coolant (that has a lower evap temperature).

 

[darkmatt]

Well... LN2 is the most effective cooling system for overclocking... Is there a place i can get it?

 

[Sin22]

It is the fastest way to get the CPU cold. To keep it cold, it is far from the most effective. It is a pain in the arse to construct and there are no commercial systems available for long/short term usage.

LN2 is utilised currently in o/cing for very very short term runs because it boils off so quickly. Basically they use a copper crucible mounted over the CPU with LN2 poured into the crucible every few seconds/minutes to replace the boiled off portion. This only lasts as long as you have Ln2 around to pour...

So, go ahead, build a big arse LN2 tank in front of your house and have it constantly being pumped over your CPU whilst in use.....

If you had read my reply carefully just now, i already mentioned that the most convenient method of getting reasonably cold CPU temperatures is to go into Phasechange. Use either one of the three commercially available phase change units out there, A) Asetek VapoChill, B) Extreme Prometia C) Frosty Chiller I think its called from HK/Taiwan.

 

[Spot]

I'd like to add a little summary

1. Pumps

High pressure, hi flow, low heat dump (you don't want another heat source). low noise. For a good price/performance ratio, Laing D5

2. Radiators

Must have low air flow resistance, ie, low flow fans, aka Silent fans, can qualify
Low water flow resistance.

Personally, I don't use the most famous brands.

3. Reservoirs

Any container, preferably one that keep the pressure in. If you need an open tub, have a considerable depth to help keep the pressure and make sure the hoses inlets and outlets and sunk at the bottom. And watch the water level.

Personally, I use a few of them in my loop that keeps the pressure in.

4. Wateblocks

No specifics. Sensitive argument here.

Basically, anything that is very resistive, make sure you get a fairly good pump.

Personally, I use Cathar's original G4


5. Tubings

To each his own.

My personal preference is Clearflex or Tygon. Good to manuver within the case and once attached to the barbs, it give a bite.

6. Coolant

Any deionised water. But personally i wouldn't mind if there's more bling bling because
I've always believe that a W/C setup is very cool looking. Those cool UV coolants looks good, but no green for me.

 

[CRViper]

Hi i was wondering if there's any difference if i were to use industrial demineralised water vs the usual distillated water?

 

[BloodRedSword]

Bro, I'm using a 400l/Hr water pump by Gigabyte, but somehow my systems are still running at around 50 degrees C... Any advice to push it down?

 

[GuOeR84]

I found 2 water cooling videos on youtube.. quite informative (at least got something visual)...

Part I

Part II

 

[aynneo]

Just curious to know if there is any big different between these 2 loop

Pump -> RAD-> CPU BLK -> NB/SB BLK -> Reservoir
Pump -> CPU Blk -> NB/SB Blk -> RAD -> Reservoir

And i see most post is Pump -> CPU Blk -> NB/SB Blk -> RAD -> Reservoir

Which one is more effective?