Fittings and Elbow Impacts

Posted: January 30, 2011 in How To & Misc

This started out as a fitting review and morphed into more of an elbow/fitting restriction guide. As most of you know…changes in system flow translates to very little CPU temperature change. This leads to the assumption that fittings and elbows have no impact to performance at all. While that’s generally true from a practical +- a degree doesn’t matter perspective, you can split hairs if you want.

So with that, I’m splitting hairs. I wanted to see what if anything I could measure between various elbows, fittings. While it is relatively insignificant, we all use these little bits and pieces, so I thought it would be worthwhile measuring what I could.

Special thanks to the many sponsors in my past testing that contributed to the various bits of fittings I’ve collected. This includes Danger Den, Bitspower, The Feser Company, Swiftech, and Koolance. Without their generosity, this review/guide would not have been possible..


In many ways, these juicy little shiny bits are like the legos of our builds. They assist in fabrication of our many ideas and serve in that critical junction between flexible tubing and rigid blocks. We also now have many compression fittings options that clean up an otherwise less than perfect zip tie or clamp,etc.

I actually tested barbs as well, but found that the differences between 1/2″ high flow barbs were too small to even properly measure. To measure differences in barbs, you would have to string 10 fold barbs together. There is a very minor loss in compression fittings however, so I’ve tried to capture that here.

Standard pressure drop except I tested on a Danger Den MC-TDX and simply switched out the inlet barb. In the end, I subtracted out the restriction of the standard barb test, giving you just the “Added” restriction over standard barbs.

I also “Attempted” a barb retention type test, but in the end found they all passed with flying colors. I was only able to test up to about 50PSI, and using as little as a single zip tie was more than enough to exceed 50PSI. Beside that, I was getting tired of getting wet! Just make sure you use clamps or zip ties, or the compression ring, and you should have no problem exceeding the rating of the tubing or most pumps. Here is a snapshot of that test, since nothing would remotely fail, I even resorted to testing without clamps…even with that, the least amount tested was still nearly 20PSI, larger barbs would get up to 30psi without any clamping.


I’m giving you both the pressure drop measured and a translation to CPU temperature gain.

This took a while and requires many assumptions, but I feel it is important to convey flow rate in terms of CPU temperature impact. Thanks to great tests like Vapor’s CPU block testing, I was able to pick a typical CPU block and estimate the change in CPU temperature due to the flow rate impacts.

The pressure drop testing was an actual measurement, but the CPU temperature results were derived by calculation based on a variety of test results and should only be used as an approximation.

I’ve just come to the conclusion that the universal language in the overclocking community is degrees I did my best to translate..


All of the barbs worked relatively the same, although I did notices slightly more retention by the longer barbs. Restriction differences were too minor to really measure with just one barb. My personal favorite is a tie between the DangerDen/Bitspower Fatboy and Hardware Labs kit barbs that came in my SR1 radiator package. D-tek barbs are another testing favorite of mine because they are a bit easier to remove 7/16″ ID tubing (My personal favorite). This just makes taking things apart while testing easier.

My favorite for function/performance would be the Koolance fittings. I like the flat spot in the threads for wrenching the barb on/off. I also prefer the flat style knurling as it’s less harsh and equally effective in giving finger grip. Finally, I just like the larger/deeper barbs on the Koolance compression best. BP and TFC probably get my pick for visual looks, but they measured a touch more restrictive and I’ve had trouble using them without resorting to some sort of pliers to remove them. Regardless, I rarely use compression fittings of any kind, and I’m a bit old school and like my barbs and clamps or zip ties.

I didn’t test too many, but the 45s as you might expect were roughly half the restriction of a 90 (Who would have guessed?..). Also using the combined compression/elbow fitting was very slightly less restriction than separate 45+compression pieces. My suggestion is to use elbows when you need them, but don’t let them become the “Spare tire in the woods” where they multiply like crazy. Tubing CAN bend you know.. Temperature has very minimial effect, but it does add restriction. One elbow on the low restriction DD MC-TDX adds almost 40% more resistance, so it will have impacts to flow rate…but it’s not going to add up to much in terms of temperature.


In the end, fittings are very much a personal preference thing. Elbows and fittings do cause some restriction, but it’s very much fractions of a degree and impacts flow rate much more than it does temperature. All of these fittings and options are winners in my book, just another color/shape lego block for you to build with. But…if performance is absolutely #1 priority, and you want to take on the hair-splitting performance alway first perspective… less is more and generally standard barbs with tubing bends and longer tubing runs will generally net you the very highest flow rates. Many people assume that tubing itself is restrictive and will assume that adding an elbow to shorten the tubing length will be a net benefit. Unfortunately, the it rarely is…one 90 elbow is about equal to 4′ of 1/2″ ID tubing so the few inches you saved is lost and then some. Do not add an elbow to save a few inches of tubing, it’s counterproductive in performance.

However, if you are building a piece of art which many people do….by all means add the fittings as needed for the cleanest possible look. Sure some extra fittings will add restriction, but it’s very minor. As the chart shows, it would take almost 30 each 90 degree elbows to add up to 1 degree in CPU temp rise. Half a dozen to get to aesthetic perfection is perfectly fine from an art priority perspective.


  1. Steven says:

    Great review! I see now there’s no need to worry about elbows for art.
    Though I’m wondering, was the non-clamped barb retention test done with warm water? Coolant in WC loops are usually warm and I wonder if that could affect the ability of the barb to stay tight overtime.

    • Martinm210 says:

      This was my first attempt at that, so I experimented around with both warm and cold water with that thought in mind. I was getting some variable results, but it seemed to be more dependent on how quickly the pressure rise was more than temperature.

      I’m sure you’re right though, I would assume as the temperature rises, the greater the flexibility in the tubing and perhaps a bit less restraint. This was really more of a fun test than anything. I was developing leaks before the tubing completely popped off too, but that was hard to watch knowing at any moment I could have a face full… I have personally experienced a leak while testing radiators using compression fittings and stiffer 1/2″ID x 3/4″OD tubing that didn’t show up until the system had come up to temperature…so I’m sure there is something to that.

      Bottom line on the retention, I’m a big fan of 7/16″ ID x 5/8″OD tubing over 1/2″ barbs for actual case routing. That along with clamps like Koolance clamps would be my recommendation based on personal use and leaks I’ve experienced. I’ve just had the least amount of trouble when I purposely go oversized on the barbs. Many of my test rigs I use 5/8″ or 3/4″ barbs purposely for this purpose. I think any of them can be made to work, but trying to quantify which of them is better is challenging and a WET challenge at that!..:)

  2. ogrefromabove says:

    I have heard that the quick-disconnects from Koolance can create a lot of restriction in a loop (depending mostly on the number of them used), would be an interesting read (IMO) to find out if this is true and how restrictive the loop can/ will get as a result.

  3. Tingez says:

    Thanks Martin i have always thought that the points you made were true and you have just confirmed my own thoughts with some hard facts.

  4. paulkon says:

    Hi Martin, if I understand correctly, the best option is to use barbs instead of compression fittings? This is great news since that will save me > 50% vs compression fittings. Is bitspower still the go to brand for barbs? Thanks!

    • Martinm210 says:

      Yeah, difference is really small, but the bitspower or Dangerden fatboy barb tested lowest in restriction if we split hairs. Several similar barbs being produced as well. Compressions are nice looking but don’t perform better. An elbow or two won’t hurt either, but a dozen starts to add up.

  5. Gabrielzm says:

    Hi Martin

    thanks a lot for another nice review. Yet the pictures seems to be broken at this time and I can not load (using Chrome and Explorer) for some time now. Can you check?


  6. lowcard says:

    What would be your recommendation for 1/2″ barbs now that Danger Den has gone out of business? Also is Primochill Advanced LRT UV tubing any good?