3/8" ID Tubing over 1/2" OD Fittings

I was reading in the classified Section on the Weapon Core I noticed Weapon Said

Weapon said:

If you are using Tygon or Clearflex, you can stretch the tubing over the next largest size barb with a little effort after wetting the inside of the tube and the outside of the fitting. This normally produces a little better flow through the core as the fitting will not be as restrictive. A ½” OD barbed fitting has an internal channel that is approximately 3/8” so it matches up with the ID of 3/8” tubing. On the other hand, it presents a restriction point if used with ½” ID tubing. A 5/8” OD barb has a ½” ID channel and works very well with ½” ID Clearflex or Tygon.

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I intend to run a 3/8" ID System since my pump has 3/8" ID Fittings. But on Blocks and Radiator, should I be getting 1/2" OD Fittings (as the option is for one the DD Site) or 3/8" OD Fittings.

EDIT: Will these fittings work with 3/8" ID Tubing, they have them on Alphacool Blocks, which I heard were pretty good.

1/4" to 10/8mm compression
1/4" to 8/6mm compression
G1/4" Push Fit (10mm OD hose)

Actually, using 3/8" ID tubing with 1/2" OD barbs would probably work quite well. There's no way you'd ever be able to pull the tubing off so you wouldn't need hose clamps, but, by the same token, you'd have to cut the tubing off if you ever wanted to change it. (I tried it this morning as an experiment: boiled some 3/8" ID 5/8" OD Tygon and fit it over a standard 1/2" OD plastic barb--the Tygon molded itself to the outside of the barb.)

As for the compression fittings, they depend on having the "proper" inside and outside diameter of tubing since the inside diameter of the tubing has to fit over the barb part and the outside of the tubing has to fit inside the diameter of the compression ring. So, you just have to do the math and see if the fittings would accept the tubing (or if you can get fittings that would accept the tubing): if you use 1/16" walled tubing you'd have 3/8" ID and 1/2" OD which would be 9.78mm ID and 12.72mm OD and if you used 1/8" walled tubing the inner diameter would stay the same but the outer diameter would be 5/8" or 15.96mm. I haven't the faintest idea of what size fittings Alphacool makes, or makes available as options, so you'd have to check on that, but the ones you listed all look too small.

FWIW, I think you'd be better off using Danger Den blocks with either 3/8" or 1/2" barbs than messing with the compression fittings, and if you used the 1/2" barbs you wouldn't need any type of clamp or fitting to secure the tubing--believe me, that sucker was not going anywhere when I tried it.

trying to fit 3/8" tubing over 1/2" barbs is a real ***** to do, even if you heat up the tubing or soak it in hot water, its still not an easy task

you'd be best off just using 3/8" fittings because thats what everything else in your system is, so running 1/2" barbs with 3/8" tubing would give you just about zero performance gain

and for the compression fittings, most times you have to run thoes with thin-walled tubing (1/16" wall), and the fittings themselves are pretty restrictive (smaller ID), so you'd be best off staying with good 'ole barbed fittings

Sneaky said:

trying to fit 3/8" tubing over 1/2" barbs is a real ***** to do, even if you heat up the tubing or soak it in hot water, its still not an easy task

you'd be best off just using 3/8" fittings because thats what everything else in your system is, so running 1/2" barbs with 3/8" tubing would give you just about zero performance gain

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I don't think the 1/2" barbs with 3/8" ID tubing would give a performance gain, but they could prevent a performance hit. Barbs generally decrease performance because they're more restrictive than the tubing. And, they're more restrictive because their inner diameter is by definition smaller than their outer diameter which fits inside the tubing. But, if one can stretch the smaller tubing over the larger barb you can avoid taking that performance hit.

3/8" ID tubing has a nominal inner diameter of .375 and a 1/2" barb has a nominal inner diameter of .368. 7/1000" is much less of a performance hit than what one would get using a 3/8" barb with a smaller inner diameter. Take a look at the pic.

Note: the only 3/8" barb I've got is the stainless one that goes to the quick disconnect on my reservoir and I doubt it's representative so I didn't bother to measure it.

Yeah, getting the tubing over the barb was a PITA even after I boiled the Tygon in water, but you can see that it did fit, that it basically molded itself to the barb, and that it isn't going anywhere.

Flow will be decreased more by the radiator and the waterblock themselves than by a 3/8" barb, so unless you feel like struggling with the hose just stick with 3/8" barbs.

I think I am feeling like struggling with the barbs, it can't hurt performance, yet it could benefit, so why not? Do the internal Diameters of the Channels in Rads differ greatly? What are they usually?

i did this with my pump. might do it with the rest of my system when i upgrade. i just heated the tube with boiling water.

no clamps!

It helps a lot to use a little bit of soapy dishwashing water just on the barbs and on the inside of the hose ends. 3/8" barbs are about to 5/16" ID. If you have 3/8" fittings on your pump, you can go with all 3/8" hose and barbs so that everything is the same size. I prefer to order 1/2" barbs where possible, and use 5/8" fittings (1/2" ID) where I need elbows. I would go with 1/2" on your blocks and rad so that if later you decide to get a different pump that has 1/2" barbs, you don't have to change out anything else, and having barbs a little larger won't hurt anything. It might actually help a little.

note just for clarification - the type of fitting I was specifically referring to in that quote are the brass ones that I use on cores. As they are brass and extremely heavy duty, they are willing to take a few passes from the polishing wheel which leaves them looking somewhat like a brass mirror on the first couple of barbs on the fitting - that slightly reduces the OD on the first 2 barbs (as well as deburring the outer edge) and makes them much slicker when damp (hence less friction for the tubing when you are pushing it over the barbs). As mentioned above, a drop of slightly soapy water makes the job much easier as long as you do not overdo it. the point was to avoid a performance hit from fittings that are more restrictive than the tubing and to get a bit better flow as a result. If the same is done with the core, the pump, etc. it is fairly noticeable. While removing the tubing takes a bit more grunting than installing it, it can be removed from polished brass barbs without having to cut it. On the other hand, tubing is cheap if you do have to cut it off plastic or brass barbs - at least it is a lot less expensive than a leak that could take out a vid card or the likes and using the smaller tubing on the larger barb is about as close as you are going to get to a 100% leak free mating between tubing and barb.

with plastic barbs, it can be a bit of a PITA but I still use the larger ones anyway. specifically, I use 5/8" OD t-fittings as some of the 1/2" OD barbed t-fittings have flow channels that are insanely restrictive and the larger opening in the top of the t-fitting makes bleeding out air bubbles just a little easier.

I used a little bit of liquid had soap to slip my tubing over the barbs and it worked like a charm. i about gave myself a hernia before I thought of using the soap. After that it was a simple twist and slip.

Rinse any excess soap away if it worries you and all is well.

Shane

reducer barbs

whitebloodcell said:

I was reading in the classified Section on the Weapon Core I noticed Weapon Said


I intend to run a 3/8" ID System since my pump has 3/8" ID Fittings. But on Blocks and Radiator, should I be getting 1/2" OD Fittings (as the option is for one the DD Site) or 3/8" OD Fittings.

EDIT: Will these fittings work with 3/8" ID Tubing, they have them on Alphacool Blocks, which I heard were pretty good.

1/4" to 10/8mm compression
1/4" to 8/6mm compression
G1/4" Push Fit (10mm OD hose)

Click to expand...

8888888888888888888888888

http://www.mcmaster.com/

Dont' stretch the tube. Reducer barbs solve that.

cathar suggested that 3/8" tubing over 1/2 barbs would reduce flow res. the transition at the connection would be smoother. so in a system with high res waterblock you would actually get lower res with 3/8 tubes than 1/2".

I've got 1/2 barbs and 3/8 tubing in my system. It was a pain getting the tubes on, let me tell you. My thumb and index fingers hurt for a couple days . Even still i think i'm moving to 1/2 Tubing soon. My lil MCP-650 is collapsing the inlet tube that got a kink in it, and i'll have to cut it off to swap. at the same time i'm just gonna move to 1/2ID for the whole system. Its about time for a flush anyways.

Don't use 1/2 or 3/8, Cathar posted that 7/16 is probably the best bet as it will fit easier than 3/8 but is closer to the ID of the barb than 1/2...

Where would I get 7/16" Tubing in the UK? Or the US if there are no UK dealers. Is there a specific model number considered best?

legendosiris said:

I've got 1/2 barbs and 3/8 tubing in my system. It was a pain getting the tubes on, let me tell you. My thumb and index fingers hurt for a couple days . Even still i think i'm moving to 1/2 Tubing soon. My lil MCP-650 is collapsing the inlet tube that got a kink in it, and i'll have to cut it off to swap. at the same time i'm just gonna move to 1/2ID for the whole system. Its about time for a flush anyways.

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when you upgrade your system to 1/2" ID tubing, make sure you get the 1/8" wall stuff - the 1/16" wall kinks REALLY, REALLY easily

Sneaky said:

when you upgrade your system to 1/2" ID tubing, make sure you get the 1/8" wall stuff - the 1/16" wall kinks REALLY, REALLY easily

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ahh thanks..i'm debating swapping up GPU blocks to a tru 1/2ID block..hrmm..more$$ heehe.

Does anyone know where I can get 7/16" ID Tubing in the UK? Or somewhere that ships to the UK? I did a google, only found Vinyl Tubing. Is that what is normally used, I was hoping for Tygon.

I found 7/16" ID Tygon here

But at £2.60 a foot is it really worth it? How much does a typical system use?

whitebloodcell said:

Does anyone know where I can get 7/16" ID Tubing in the UK? Or somewhere that ships to the UK? I did a google, only found Vinyl Tubing. Is that what is normally used, I was hoping for Tygon.

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i believe this is where Cathar got his from (T600-26)
http://www.mgscientific.com/pricequote/group.asp?GROUP_ID=8510

looks like you have to order 50 feet (though i imagine you could easily dispose of the surplus....)