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Since most waterblocks have a 1/4 thread, why use a 1/2 hose?! less kink?

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ntino

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Mar 18, 2010
Also, why then are high flow pumps used? 1/4 is a really small diameter, and you need a high pressure pump, yet most recommend the 655 over 355?

Sorry for the noob questions, just wanna make sure i understand whats what.
 
Also, why then are high flow pumps used? 1/4 is a really small diameter, and you need a high pressure pump, yet most recommend the 655 over 355?

Sorry for the noob questions, just wanna make sure i understand whats what.

I think you may be reading the threading type (Commonly G 1/4"). This isn't the size of the fitting, just the thread type.
 
wrong what I understand, 1/4 IS the thread diameter, unless i am missing something.

For example, the 1/2 ID barb screws into a 1/4 NPT or G 1/4" so the outside of it is 1/2 but the inside is in effect 1/4...
 
i measure 3/8"opening in a standard barb, fat boys are even bigger.

and the G1/4" opening being 1/2"

barb.jpg
 
G1/4 is the thread "type". I know its missleading ...

An 1/2 fittings is 1/2 OUT and as spawn just post, in lots of case, ~3/8 inch.
 
thats what I thought - clearly it cannot be 1/2 inside if its 1/2 outside, therefore you could use 3/8 tubes as long as you can fit them onto the 1/2...(which is not that hard if you have the right material and hot water) VERY hard if its the wrong material. I do realise that one should still use 1/2, but was under the impression that the actual opening that the barb screws into is 1/4... so it made no sense to me :)

Sorry for being confused guys... I come from a world of aquariums and there, the thread size is always referred to as the inside diameter of the tube.

Thanks for the help!

On a side note, is it true that a properly mounted 355 with external res mod makes no noise? I am having trouble deciding whether to get that or a mcp655, I am going with a HW 560 GTX for my rad because I found one on ebay new for $130 shipped.
Dont want to end up with a noisier than needed pump, and swiftech say that the 355 is noisier, true?
I have read people saying both.
 
I have 2 MCP655 at full speed and i cant hear them ... All my fans are on fan controller. My comp is very silent. I dont think you have to be woried about pump noise.

The GTX560 is a BIG rad .. I dont know a normal case that can fit this RAD inside !
 
the rad will be mounted outside of the case for better temps(you are in effect heating up your case by using the rad inside of it). I still have to come up with a way to mount it on the outside, any ideas?
 
what did you use to mount it? rad mount from swifttech? these are for 120mm... not gonna fit the holes on the 140 i think. also, what do you think of the vario vs 355 with top?
 
i think i understand what you really want to know.
the answer is resistance is cumulative throughout the loop so the smallest diameter the water travels through isnt going to set the whole loop at one resistance.

play with this for a bit till it really starts to take hold

http://home.earthlink.net/~mmc1919/venturi.html

"he answer is resistance is cumulative throughout the loop so the smallest diameter the water travels through isnt going to set the whole loop at one resistance." - Yes, thats true, but that one small diameter puts alot of resistance on the whole loop - think about it, if you had to squeeze water through a needle hole, do you really think that water would come out at 300gph per pump specs(no tubes, just the pump and the hole) ? think about :)

The problem with that link is that its a model for "ideal fluid" and ideal meterial, which can contract and expand indefinetly - all that tells you is just an illustrative of the volume and flow principles.

Water and the material it passes through in our case are not ideal, far from it, and a restriction does create quite a lot of head pressure. I have a 600g aquarium with over 15000GPH of water going through it, using different pumps, ect. and therefor am fairly familiar with flow restrictions - these matter a lot, and the more flow you have through a system, the more restriction that system poses, so if you pump at a 100gph through a system and it offers a restriction of 4 feet of head (which is roughly 1.5PSI), pumping at 500gph through that same system will yield more resistance (this of course varies with systems, so for example, pumping water at 100gph through a 1" pipe will yield little resistance, doing the same at 10000gph will be very different.

from experience, 1/2 pipes are well suited for anything up to 400gph, but using components that have much less throughput will restrict flow tremendously.

Go here to see how much the diameter of a pipe through which water flow matters
http://www.anzcp.org/CCP/Physics&Chem/Flow & resistance of fluid in a tube.htm

These are formulas of laminar flow.
 
there is flow... the lesser the size of the pipe the more head you need to move water at a certain velocity...

you could move 80-100 gph with no problems through 1/4, in fact, from what I have seen, 1/4 would be more suited to this application, becuase most of the restriction comes from the waterblocks themselves, not the pipe.
 
the rad will be mounted outside of the case for better temps(you are in effect heating up your case by using the rad inside of it). I still have to come up with a way to mount it on the outside, any ideas?

That all depends on where the rad is mounted, which way your fans are blowing, and the case design.

what do you think of the vario vs 355 with top?

Both pumps are good, reliable pumps. The D5 is of course larger and prefers lower restriction setups, whereas the MCP355 with top has better head pressure and can result in better flow in setups with a bit more restriction. People also of course like the fact that the vario has the built-in rheostat to vary the pump speed. There's not going to be much of a difference performance-wise in most setups. I prefer the smaller size of the MCP355 with top myself.

therefore you could use 3/8 tubes as long as you can fit them onto the 1/2...(which is not that hard if you have the right material and hot water)

While it is possible, it is very hard to get 3/8"ID tubing onto 1/2" Bitspower barbs. Most of us will use 7/16"ID tubing for that. 7/16"ID 5/8"OD also offers a nice compromise between offering very low restriction from the tubing diameter itself with ease of routing, yet it seals very tightly onto these barbs.

On a side note, is it true that a properly mounted 355 with external res mod makes no noise? I am having trouble deciding whether to get that or a mcp655, I am going with a HW 560 GTX for my rad because I found one on ebay new for $130 shipped.
Dont want to end up with a noisier than needed pump, and swiftech say that the 355 is noisier, true?
I have read people saying both.

The MCP355 is a quiet pump when mounted on something to completely isolate pump vibrations from the case. Petrastechshop.com gel stuff is a wonderful solution for this. As for the noise, it really depends on how sensitive you are to noise and pitch. Whereas the D5 can be dialed down, the MCP355 can't without an external rheostat or beefy fan controller. Both have a degree of high-pitched whine to them. I personally would use the MCP350 with top myself as it is quieter than the 355 yet still sufficient for CPU/GPU setups. I personally am very sensitive to pitch and have moved to an Aquastream XT which is about as quiet of a pump as you are going to get.

One note that I will make about your 1/4"ID tubing post. There is no reason to introduce unnecessary restriction into a loop from tubing. Most will recommend not going less than 3/8"ID for this reason.

Regarding the rad, while there is of course nothing wrong with 140mm rads, the available selection of fans is very limited at best. For $100, I can buy 2 MCR320 rads and get some really good quiet fans like Gentletyphoons.
 
but how does this equate to what you just said.....

Simple, I said that 1/4 would be a decent size to allow for enough flow in watercooling applications - I didnt say it wouldnt restrict the flow of a big pump - it would, in fact, idealy you would use a low flow high pressure pump, such as the 355 - which is why it comes with 3/8 in stock form, modding it just makes it into a higher flow pump but with less head.

Think back to my needle hole analogy - flow lost there will not be regained( - its an extreme example but its true in our applications - if you have a component in your system which is restrictive - it will restrict the system as a whole - if its a linear system.

An even easier example would be this - imagine your kitchen sink - you use a ball valve to control how much water comes out(effectively changing the diameter of the flow pipe in just 1 tiny spot - you are able to do it easily despite the fact that water pressure in houses in the USA is anywhere from 40 to 65 PSI, thats 90 to 160 feet of head!!! Surely you will admit that filling a bucket with water from your kitchen sink takes a very different amount of time depending on how much you open the kitchen sink valve - this is changing flow rate based on 1 restriction in a system with 10 times the head of your average pump - now imagine what it does to a pump that tops out at 4-8 PSI e.i. nearly no flow at that PSI)

to fight that, you can design a system that will work in parallel and add some ball valves(or even better, gate valves) to control how much flow is dedicated to each component.

I know I am new to watercooling, but not new to water or plumbing, and my opinion probably does not carry enough authority, however, just to point out - I probably have a lot more experience when to comes plumbing and water, hoses, ect than most on this forum.

here are a few links to my creations :)

The basement portion of my saltwater tank:

http://picasaweb.google.com/lh/photo/1DUVWot81eQK9_4z7Pcs7A?feat=directlink



Plumbing for a planted freshwater tank:

http://carsofnortheast.com/discus/cubeplumbing.jpg
 
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Simple, I said that 1/4 would be a decent size to allow for enough flow in watercooling applications - I didnt say it wouldnt restrict the flow of a big pump - it would, in fact, idealy you would use a low flow high pressure pump, such as the 355 - which is why it comes with 3/8 in stock form, modding it just makes it into a higher flow pump but with less head.
Not quite true. Have a look at this P/Q curve graph. For all but one of those aftermarket tops the stock top has higher pressure....but only below 1.0GPM (less than that isn't ideal for our purposes). Above that, all of them produce more pressure per flow than the stock top. Here's a link to the whole article. Well worth a read.
 
Not quite true. Have a look at this P/Q curve graph. For all but one of those aftermarket tops the stock top has higher pressure....but only below 1.0GPM (less than that isn't ideal for our purposes). Above that, all of them produce more pressure per flow than the stock top. Here's a link to the whole article. Well worth a read.

Yeah, i see that, must be a flaw in pump design, maybe bad materials turbulence that works against the impeller adding to restriction...
 
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