 What tubing size should I buy? Well, even though water cooling legend Cathar addressed this once and for all over a decade ago, it is still a topic of debate in PC and liquid cooling groups. So we are going to find out. So my answer to this question for the last six or seven years has been 3 1⁄8 inch ID. So that's short for inner diameter, 5 1⁄8 inch OD. So that's for outer diameter and usually from Primochill in whatever color your heart desires. Their tubing's pretty good stuff. And it's been my belief that any bigger than this will make no difference to your system temperatures. However, I do have to confess that I have never actually grabbed some big old, thick old tubing and tested this in a controlled experiment. So it is time to change that. First, we're gonna need a few things. Intel Extreme Edition 5960X, check. Three different diameters of tubing, check. A triple 120 millimeter radiator, check. EKS supremacy Evo CP block, check. Fittings, check. And check, check. And the optimal footwear for science, extra check. Pose. Oh right, the last thing we need. This is a flow meter. This will allow us to measure the flow rate of our different loops. And a shout out to the guys over at Performance PCs for sending this over to us on super short notice. Now, as much as I love to spend my day building, testing and tearing down various water cooling loops with different tubing sizes, there is a reason that I hired writers. So I'm gonna let Jake take care of that while I go do very important CEO stufes. Really, you put stufes in there. Yeah, no, you put stufes in there. Oh, sure. It said stuff before. Okay, sure, whatever. Ha ha, the joke's on me, I guess, because I still have to record this narration. So then, to keep our testing relevant to the real world, all of the loops were built into an actual case. The fractal design define R5. So to establish a baseline, we're starting with a typical configuration. So we've got our pump going out to our CPU over to our radiator, and then back to our pump, which has a reservoir built into it. The whole thing is running 3 1⁄8 inch ID, 5 1⁄8 inch OD clear tubing from Primochill. As for coolant, we're just using plain Jane water, which is gonna be replaced for each one of our tests. I mean, not because we would expect that new water would affect the results, it's just because recapturing and reusing it would actually be very inconvenient. That is how you fill a water cooling loop. Good thing, bro. So to put a little bit of extra heat into our loop, this will help to separate the performance between the different tubing sizes. We're gonna set it up at four gigahertz with 1.15 volts. It's not like an impressive overclock for a 5960X, but it should be stable, and really that's all that we need for this kind of an experiment. All right, so let's get Ida going. Ah, stress FPU, and bippity boppity, we will be back in a while. We ran each of our tests for a good chunk of time. Start a 15 minute timer. And then we reset the statistics, collecting them over a three minute window to get meaningful averages. In between our 50% and 100% pump speed tests, we allowed a grace period of 10 minutes with the fans on full blast to cool our water back to ambient. After the first set was done, the process was repeated with 12 millimeter inner diameter tubing, and then 13 millimeter inner diameter. Okay, so, you made quite a mess here. Yeah, okay. How are our results then? Well, they're a little depressing. They're all within margin of error, and I didn't even get to use the flow meter because there's no way to get any results from the RPM that it reads. No liters per gallon or liters per gallon, liters per hour. So it's just an RPM? Yeah, it's just an RPM. Oh. Yeah. So what, it's just no difference? Yeah, it's no difference. What, why are you going over there? Hey, stay away from that. What are you, what are you? Wait a minute. Wait, wait, hey! I knew it! You weren't supposed to see that. It's the workshop! All right, so you had your fun, Jake. So, back in the early days of water cooling, enthusiasts would often repurpose aquarium pumps, which are optimized for flow rate and not head pressure. So using wider diameter tubing could make a big difference. But thanks to more pressure optimized pumps like the D5 and the DDC, even if this might not seem intuitive, even dropping down to like a 10 millimeter diameter is a non-issue. I mean, even quarter inch, which the most basic all-in-one water coolers use should not affect the performance of a modern loop in any way other than the bend radius of the tubing. So in most cases, it's far more important to consider other things like the restriction of your water blocks, any tight bends, the inclusion of restrictive fittings like quick connects. But even in this worst case scenario, which we actually built fairly recently, the D5 didn't break a sweat. So the final answer then, what tubing do you buy? Well, it's the good old same answer that we started out with. Any good quality tubing like Primochill or EK in 10 millimeter inner, that would be 3 eighths inch, or 16 millimeter outer diameter, that's 5 eighths inch for our Yankee friends. And the thicker the wall, the kind of better, because it'll help with any kinking in your bends if you don't wanna use angled fittings like we've done on some of our builds. So thanks for watching guys. If this video sucked, you know what to do. But if it was awesome, hit that like button, get subscribed or check out the link to where to buy the stuff we featured in the video description. Also linked down there is our merch storage has cool shirts like this one and our community forum, which you should totally join. Workshop. Get that out of here. I like it, it's pretty nice. Actually, you know what? We should probably put it up. We should put this in Luke's office. How about like right here? Oh, man, you're just gonna hold it up there. That seems to be perfect. How about like right there? That's pretty cool, right? An orange will never look good. I don't know.