7/16" ID (5/8" OD) tubing - ultimate size cross-over?
 

Been rolling the whole tubing size idea around in my head, and thinking about trade-offs and the like.

I like the idea of 3/8" ID tubing, but I just can't shake the feeling that for >4LPM that it starts to become an increasingly significant source of restriction for those who wish to make use of strong pumps capable of pushing the higher flow rates. It's not that 3/8" tubing is bad at all for coping with moderate flow rates, it's just that it could be better. For example at 6LPM, 7' of 3/8" ID tubing is offering pretty close to 1mH2O of pressure drop all by itself.

But 3/8" is attractive because it's very light, and it bleeds air-bubbles fast.

1/2" tubing is fat and unattractive. Unless flow rates are getting past the 6LPM mark, air-bubbles don't bleed very well. It's heavy, and it requires fairly thick walls (1/8") before it can turn good radii without kinking, but this wall thickness comes at a cost of making it stiffer to turn, thus putting more leverage on the water-block's all important thermal contact. However, it takes around 13.5LPM before 7' of 1/2" ID tubing offers 1mH2O of pressure drop, so really it's almost overkill.

So I looked to the middle-ground, that being 7/16" (~11.1mm) that has 3/32" wall thickness for a total of 5/8" OD. Per length of tubing it's about 2/3's the weight of the 1/2" ID (3/4" OD) tubing. Being a thinner ID it is able to be bent into tighter radii without kinking, allowing for the use of the 3/32" wall thickness, which means that it also becomes easier to turn those radii. It offers 1mH2O of pressure drop at 9.5LPM for a 7' length, which pretty much puts it still as a very attractive offering.

Then I took into account stretching the 7/16" ID tubing over 1/2" OD fittings (barbs) with 10mm ID orifices. Due to the "lip effect" the 1/2" ID tubing actually offers nearly 3x the transitioning resistance at fittings as the 7/16" tubing whose ID more closely matches the ID of the fitting. Over a typical full system when fitting resistance is taken into account, the 7/16" ID tubing offers almost the same amount of tubing + fitting resistance as the 1/2" ID tubing.

Results were obtained using the pressure drop calculator from http://www.pressure-drop.org.

This all got me to thinking that really what us 1/2 inchers may really want to be doing is fitting 3/32" thickness walled 7/16" ID tubing over our 1/2" barbed systems, and pretty much be enjoying no extra system resistance, but gaining the benefits of lighter tubing that is easier to bleed (bleeds very well at a predicted ~5LPM), easier to bend, isn't as bulky, "hangs" less off water-blocks, and is significantly cheaper due to less wall material being used.

is 7/16 any tougher to find or more expensive than 1/2"?

McMaster item #5233K44. $.36 / ft. They have other types w/ same size... Might have to get some and try them out:)

So this would be overkill? --
http://cgi.ebay.com/ws/eBayISAPI.dll...DVW#ToPictures

Hrm.. I like the idea of 7/16 tubing.. in my most recent rig.. had 2 issues where slightly smaller tubing could have been much easier than attacking the case with a dremel. Currently using Clearflex 60 1/2" ID 5/8"OD over 5/8" barbs..

I will be making a new system for a neighbor in a week or so.. might have to try to 7/16 tubing.. 1/2" brass barbs all around could save a little weight.. lan portability is getting questionable for my main pc..


Cathar.. plz ;) I would like to preorder 5 of the production Storm blocks.. ;) I need 3 for amd64 2 for xp ;D

~

How hard was it to install the 7/16ID tubing over 1/2 OD barbs? This sounds like a good idea.

I've tried installing 3/8ID (1/2OD) tubing over 1/2OD barbs and that didn't work at all; the tubing wall wasn't thick enough to push it over the barb after being heated with hot water.

could you also put is on smaller 3/8" od barbs aswell?

I'm guessing no,but it would be kinda cool if you easily could mix and match wc'ing items with different barbs on them.

Of course. You would have to clamp it very tightly though. I have had a good experience clamping 1/2" tubing on 3/8" fittings when need be.

...but that's not usually recomended, simply because the tube can kink over the barb when clamped, which would more than likely leak. Just be on the lookout for it, if you have to go that route.

I would double clap it if i did.

link is dead atm, anyway, the only other "midway" size I see is 10mm, how would that compare?

I managed to find 7/16" ID (5/8" OD) Tygon R-3603 tubing here for a decent price:

http://www.mgscientific.com/pricequo...?GROUP_ID=8510

Wow.... that's pretty good. Anyone here wanna split some?

I'm personally up for 25' of the stuff, so if anyone in the USA wants nut out a group order, put me down for that much.

Just to be perfectly clear, we're looking at item code: T600-26

if enough people would be interested, I would buy it. i'd use about 8 feet of tubing.

Excellent idea Cathar. While we're nit picking, has anyone gave a thought to the total length of hose barbs used in the typical system? The average 1/2" hose barb length is 1.75" with a 3/8" ID. The typical system has atleast 8 of these. 8X1.75=14" - 1foot,2inches. Add in a GPU or NB and your at 21" - 1foot, 9inches. Almost 2 feet of 3/8" ID. there. We all know that the total flow for a system is the sum of it's parts. Now that I'v been thinking more about this since you brought up this 7/16" ID. tubing; The push quick connects like Swiftech uses seems more attractive to me now. They use them for a reason other than ease of use. Maybe replacing all hose barbs for quick connects will make up the difference for using 7/16"ID. tubing? I can't get to the pressure drop calc you used. I can't connect to it.

3/8" ID barbs or 3/8" ID system. Make your choice. Too bad that 5/8" quick connects weren't available, though. The barbs add no total length to the waterpath, BTW, as if you didn't have them you'd need 1 foot, 2 inches more tubing...

I've tried to find 5/8" quick connects with no luck. 1/2" quick connects can be had but hard to find. With barbs, i'm not talking about total length of the water path. With the normal 1/2" hose barbs you have a total of 1 foot, 2 inch path that is actually 3/8"ID compared to the 1/2"ID tubing. What I'm getting at, is removing that 1 foot, 2 inches of 3/8"ID restriction. By removing that 1 foot, 2 inches of 3/8" restriction, I would get the same amount of flow as if I used the 7/16" tubing. If your using 3/8" ID tubing like me, that equates to 1 foot 2 inches of 1/4"ID restriction. In my case it's a bit more than that though.

Like I said, Swiftech does it for a reason.

My bad, removing that restriction in a typical 3/8" system would not bring it anywhere close to a system using 1/2" barbs with 7/16" tubing. I havn't got a decent calc to use to get it perfect and worth qouting here.

What I came up with so correct me if anyone likes to. This is not counting the block's or rads, Just the tubing, hose bards and or quick connects at 3lpm.

The typical 1/2 system with 4ft of tubing has a pressure loss of .0031 bar.
Replace the barbs with quick connects and it's 0.0013 bar.
With 7/16 tubing it's .00435 bar.

Your not losing much using the 7/16" tubing.

The typical 3/8" system with 4ft of tubing has a pressure loss of .01715 bar.
Without the hose barbs and replaced with quick connects it's .0147 bar.

So there's the difference that I came up with. I havn't done anything with bigger pumps, say around 6lpm yet or replacing the hose barbs in place of quick connects in the 1/2" system. With a 1/4" system, it's pretty dramatic.

After looking close to all of this and going over it multiple times I come to a conclusion. With 1/4", 3/8", 7/16" and 1/2" ID tubing, the flow rate is pretty close to each other until you get into some ungodly amount of flow from a huge pump. The thing that caught my attention was the pressure drop. Between 3/8", 7/16" and 1/2" the pressure drop was there but not to negligable to be concerned about. Velocity increased for each one with 1/4" being the highest. This leads me to think the reason 3/8" isn't terribly worse than 1/2" because of the increase in velocity - Velocity makes up the difference. Here's what really caught my interest. Going to 1/4" velocity increased more than double, reynolds increased dramatically but the pressure drop was just to much to even consider using 1/4" tubing. So much it can't overcome the increased boundary layer effect with heavy cpu loads we see. The reason why the noticable high temps on 100% cpu loads.

My conclusion is; flow rate isn't everything if you havn't got the muscle (pressure) to do anything with the flow rate. Which has me questioning why the Euro guys even bother to consider 1/4" ID even in a low flow situation.

Am I going in the right direction with this? Any corrections or arguments?

Hey Cathar, quick question for you: Were you able to get this stuff to stretch over 3/4" barbs at all?

I wonder if this 1/16 wall tygon would hold up? Stock 57118 7/16 ID X 9/16 OD @ 1$.58 foot. It has a lower PSI rating - 16 psi @73°F.

I finally got some delivered last week.

No - no chance of it stretching over 3/4" barbs. Would stretch over 5/8" barbs at best.

Hows it working for you? much easier than 1/2"?

I think you'd kink it pretty easily... but you don' t know unless you try!

Ive been using 7/16 in my setup for a few months now and it performs as well as the 1/2 I replaced. There was no change in temps what so ever and it was a bit easier to plumb. The one problem you will have is not getting the 7/16 over 1/2 barbs but getting it off which is next to impossible. I have to slive it off the barbs in order to remove it. You will also have to work it a bit to make it slip over the d4 inlets if you have that pump, since they have that rig.