TGAlex

I think I got it, thanks. Two pumps can handle higher head pressure but for actual flow rate to increase, you'd need a pump that can operate at higher rpms. Academically speaking of course, as it's not needed in a computer loop. Yes running a 2nd pump with no reservoir is probably better, technically. But I have to admit, I also liked how they looked together. Got the idea from the Corsair site. I don't think I'm going to make any changes in the near future to be honest, but splitting the loop sounds like a great idea. I'll get to keep the two reservoirs next to each other too that I want for aesthetic reasons. I may go for it when it's time to check the o-rings.

Maybe you're right, I dunno, you seem pretty certain. Just went with two for peace of mind. Though, running two, doesn't that mean they can provide the same flow at lower rpms and therefore wear out slower? Yeah I was once tempted to tweak the voltage after watching a JTC video, I'm sure you know which one I'm referring to, but I totally chickened out and I feel absolutely no shame to admit it. 🤣

You know what, it kept bothering me as well, but honestly? Let's look at the facts here. This is hardly the weakest spot for a leak, when you have 20 90° fittings in the loop (90° = resistance and 20 of those = great resistance). Obviously you have far less of those, but still, pressure against the filler cap is nowhere near that. Furthermore, the filler caps themselves use the exact same o-rings as the fittings and they screw in the exact same way. It's why I ended up not replacing them with an XF valve after all, which I thought would provide better safety at first. It wouldn't. There was no point. Last, if you leak test the loop beforehand and no air escapes at like 10 psi for 30 minutes, there is no way coolant will, and certainly not from the filler cap. However, as with all loops, whether you have 20 90° fittings or none, whether you're cooling 1 component or 5, you need to check your o-rings every couple of years. Just take the chance to do that right after a full drainage. Unscrew each fitting, check, screw back if ok, have any doubts, replace o-ring, simple as that. So that being said, I did nothing, just totally ignored it. I know that's probably not what you wanted to hear, sorry. 🙁 Last, for what it's worth, with the PC turned off, unscrewing the right hand side reservoir's filler cap first, makes no real change to the coolant level. Then, unscrewing the left hand side cap causes the left hand side reservoir's coolant level to drop, while the right hand side goes up, until they are the same level.

The following is playing Assassins's Creed Mirage in 4K and all settings maxed out. Note that the CPU load shows 1%, just like the PSU shows 200 something watts but that's because I wasn't quick enough to capture the screenshot. That said, it's a GPU intensive game anyway. So that's 40C coolant at a maximum 3700rpm pump and 900rpm fans. 3k could probably be enough for the pumps but honestly I can't hear them while playing a game so why not, and the same goes for the fans. Room temp ~ 24-25C and the case really does considerably lift the room temp all by itself, you can feel it just walking into the room. And as you all know, when you notice heat coming out of your case which increases as load increases such as when playing a graphics intensive game, that is a clear indication that your loop, or whatever it is that you're running for heat dissipation, is doing its job. In Cyberpunk 2077 both GPU and CPU temps, and coolant of course (and room temp lol) are slightly higher.

Sorry for the late reply. No I didn't, just topped up the first reservoir too as it was getting on my nerves being halfway full, at least they are now about the same level. One other thing I forgot to mention is that the inverse correlation between the two reservoirs keeps going indefinitely, I assume until the second reservoir eventually reaches the nearest to the top. Every time the loop is ran, coolant level will keep doing its thing, just takes quite a while until you notice a significant difference. On that PC I'm mostly in the weekends (use another one the rest of the week), say about 8 hours for the entire weekend. At that rate, takes about a month until you notice a 1/4 of an inch coolant level difference in either reservoir. So what I think happens into the second reservoir is that that little air pocket keeps being positive pressurized little by little, with coolant taking up its space, until it reaches a max pressure point (as per the pumps capacity), which I still haven't identified but is definitely under 1/2 an inch. The first reservoir should be on negative pressure as coolant goes down at the same rate. Last time coolants got there I unscrewed the caps a little (both reservoirs) with the PC off, which relieved pressure and vacuum respectively off the reservoirs and brought them to default levels. You know what I think? If I have to do that like once a month, I guess it's no big deal, but honestly if air doesn't escape the cap, which it doesn't (leak tested the loop beforehand), water shouldn't either, so might as well just let it reach as high as it can. Definitely isn't going to reach the top, cause air isn't going anywhere, and two D5's can't build more pressure than my leak test so I shouldn't worry about the cap either. Still thinking that perhaps an XF valve in place of the cap, might offer some extra safety (still place the cap on the other end). But do I really need it? Probably not. And life goes on... As I said, ended up topping up the first reservoir too, cause at least it now looks good. That looks smart, guess I could've fitted that instead and saved me from the coolant level trouble, but oh well... Going to post some pics in a few minutes. You'll notice the 90 degree restrictions all over the loop (just didn't wanna get into bending), the flow indicator and filter, plus 4 radiators (2 x 480 and 2 x 360), an XG7 RGB 30 series TUF block for the ASUS 3090 TI OC, ASUS Maximus Extreme Glacial's massive block that cools nearly the entire MB including the 13900KS CPU which is notorious for running hot so I needed to maintain a minimum flow at reasonable rpm (I know fan speed is more important at keeping coolant temps in check, but minimum flow was also a concern). I doubt a single D5 would keep up except maybe if running maxed out, which I didn't want. That, including having an extra pump as back-up was what I was after. Pics in a while...

Alright, I'll post back when I've ran my tests. Thanks for your help.

In case you're wondering, it's a Category 5 into the case, I had a hard time keeping my paper towels in place while I was leak testing the loop. And that's no joke. If you're up for serious work on cable management, and I do mean serious, go for push-pull on all 4 radiators (with your custom made top bracket), that's 28 120mm fans in total. You'll be blown away. Actually literally.

Hi there, I don't see how they can fit, and you have that box thing which I never figured how to put out of the way, ended up using it to my advantage so right now I'm happy it exists, never thought I would say that as I used to hate it. I don't know if improving air flow into your case is all you want, but would be a lot easier to add three on top if you just find somebody to 3D print a custom bracket for you, that's what I did. And that being said, you can add a second radiator on top. Cheap and easy fix. Fan extension cables was my second best friend btw.

Thanks for your reply. So topping up the second reservoir isn't going to make any significant difference with respect to pressure. Perhaps I could just add a finger just so the first reservoir doesn't go too low, but still keep the second reservoir about an inch below the top. Yes I figured that one pump might've been enough but I think barely. It's quite a big loop with a ridiculous number of restrictions, I'll post a few pics soon. If one pump could really handle the flow, chances are it would need to operate north of 4k rpm at all times, and probably max out under heavy load and as you just said, I was looking for a quiet operation. Still haven't installed iCUE, but I'm hoping the two pumps will provide good flow under 3k, ideally 2.5. Also, the radiators are massive and the 120mm fans are in push-pull configuration (2x8 so that's 16 fans in front and 2x6 that's 12 on top) which means neither the pumps nor the fans may ever need to operate beyond 60%, no matter the load. Of course that's yet to be tested, but that's why I went for such a cooling capacity. One other reason I went for a dual rather than single XD5 was to have a back up. Still trying to figure why three days later the first reservoir resembles a transparent can of sparkling Evian while the second is pure mineral.

So after several months working on my latest build, placing several orders for new parts and dealing with shortages in between, as well as having to work around a number of problems that arose throughout the build, I have finally put it all together and it's running like a charm. Never thought I would be able to fully occupy an Obsidian Series 1000D but turns out I have. More on that build soon, for now I need some help with running two XD5 pumps, with their reservoirs. Two things before I begin, one, I still haven't installed iCUE so the pumps are running in full speed (PWM disconnected), that's next on my list, had a ton of stuff to do, and second, I have already searched online and have found a few posts on different forums, and more or less they are all in line with that it's best to run a single reservoir, although two would work too. Now, I'm not interested in changing my reservoir configuration, unless there is a really good reason to do so, but I'd like to maximize the pumps' efficiency. So, the pumps/reservoirs are connected with an adjustable Aqualink pipe that sits horizontally, length set to about an inch, plus a short male to female extender fitting to get my precise length, and connects to a 90 degree Corsair fitting on each reservoir, that's to give you an idea of how close the two pumps are, very close. Running 5L/minute on a 4 rad configuration (2x480 and 2x360), plus Maximus Extreme Glacial's massive block for the cpu and XG7 RGB 30 series TUF block, and a good number of 90 degree fittings throughout the loop, which I think is pretty decent flow. Now, both reservoirs are halfway full, when the pc is off, and when I turn it on, the first reservoir loses a bit of coolant (level goes down by about half an inch) which goes into the second reservoir and gains that little extra. According to what I've read online, although there is nothing wrong about this, I mean the loop will still work fine (and it does, as said previously), it will not allow the first pump to run at full efficiency, as it also needs to compress the air that sits over the second reservoir. To fix that, I'm supposed to fill the second reservoir all the way to the top, tightly seal it, and that way the first pump can build liquid pressure into the second reservoir that from now on will act like a water block, effectively moving full liquid pressure into the second pump and then into the loop. Do I understand it correctly? And obviously no need to top up the first reservoir, that can be filled just like you would normally do in a single pump setup. What I would like to know is, exactly what kind of efficiency am I losing right now? Is it like 5%, 10%? How much gain are we looking at, if I top up the second reservoir? Also, you know, turning the second reservoir into a water block kind of worries me, so I was wondering, if I ended up doing that, instead of using the reservoir's plug, would it be more reliable if I fitted a short male to male extender on it, then XF ball valve and then the plug? That way I would have both the valve and a plug at the end, just for peace of mind. Do you think that makes sense? And that being said, I assume the valve is designed to handle the pressure? One last thing, I've noticed the first reservoir is full of little bubbles that don't seem to go away at all (been a couple of days) while there are no bubbles on the second, literally none. How would you explain that? Thank you guys, long post I know, sorryyy...

I get what you're saying, it makes perfect sense, but would such a massive bubble trigger a fail safe causing the pump to operate at 800 rpm? Though it was a hit or miss kind of thing, it was all normal until shutting it down, next time it was at 800, then back to normal and so on. So perhaps it was marginally causing a fail safe is what I'm wondering. Or could it be causing a vacuum, which would again trigger a fail safe? These stress tests were done last night and this morning, nearly two weeks after having gotten rid of the bubble which was a day or so after your Nov 5 post.

Also, following your suggestions, I have found the exact minimum speed that the pump needs to run to provide sufficient flow, and that is roughly 2800rpm. I did both ways, from top to bottom and vice versa and it appears below 2800 CPU temp was rising and coolant dropping, which was an indication of insufficient flow and my explanation is that coolant was lingering in the CPU block a little longer and the sensor was detecting lowering temps because heat wasn't being transferred sufficiently into the loop, which is what you mentioned at the beginning of your Nov 3 post @c-attack. At 3200 rpm and higher it was performing better but then noise started outweighing the benefit. 3000 rpm is just perfect, it works and I can hardly hear it. No need for a flow meter at this point. 🙂 Oh and I got news about the low rpm issues which was one of the two reasons I created the thread. Yeah, I dunno if this is a technically valid explanation, but first let me say that it's all been normal for a good two weeks, since I finally got rid of a huge air bubble that I think was stuck somewhere at the top radiator for like months! See my top radiator to radiator tube? After shaking the thing like I was making cream, and at the same time having the pump at full speed, I finally saw a bubble so big that expanded through half that tube. After giving it a little more shaking, making butter at this point, the bubble finally showed up at the last tube and landed in my reservoir causing a mini explosion. Well that was like two weeks ago, and haven't had a low 800 rpm issue since. Coincidence?

Thank you both for your suggestions. I also downloaded FurMark which is one of the most intensive GPU stress tests. Here are my results. Idle @ 23C ambient CPU stress @ 100% for 20 minutes. I don't think coolant would ever reach 30C honestly. By the time I took the screenshot, it was already looking nearly stable. CPU was hovering around 54 and 55C the entire time. Easy peasy. GPU stress @ 100% for 20 minutes @ 2560x1440. This time coolant got up to 31C but struggled after that. At 32.75C when I took the screenshot, it was looking nearly stable. Of course pump and fan speed increase kicked in after 30C which certainly helped keep coolant temp from rising at a faster pace. GPU made a quick jump to 55C iirc and then crawled forward to eventually stop at 60C. Maybe after another 20 minutes it would've got to 61C. Of course the card is both water and air cooled and the fans were already picking up, although still under 50% at the time of the screenshot. So we're talking +4.5C coolant compared to the CPU stress. CPU + GPU stress @ 100% simultaneously for 15 minutes, the ultimate challenge. Coolant got up to about the same temp as that of the GPU stress, but 5 minutes earlier and looking at the timeline you can see it's not yet struggling, but not exactly going through the roof either. Perhaps it would begin to struggle once pump and fans turned it up a notch, like at 34 or 35C. Of course, just how often would you see 100% load in both the CPU and GPU simultaneously?

Thanks for your reply. Changed sensor to coolant temp as you suggested. I'm sticking with custom curves but changed to: Fans: 750rpm up to 30C and 1150rpm (full speed) at 40C. Pump: 3200rpm up to 30C and 4800rpm (full speed) at 40C. At ambient 24C, idle coolant temp is about 28C and considering it took a whole hour at 90% CPU load for it to climb by just 4C, there should be no serious fan or pump speed increase unless the GPU joins in. But even so, I believe I will be hard pressed to get coolant temp to rise above 35C (950rpm and 4000rpm respectively). This way I'm maintaining a narrow range for both, which at the same time ensures a quiet operation. The reason I've set the pump to start at no less than 3200rpm is that I believe there isn't enough flow below 3k, but looking to install a flow meter to make sure.

Hi there. Well I didn't contact support as couple of weeks after my last post the noise was gone and never came back. I now have a pretty good idea of what was causing it. What I forgot to mention as I didn't think it had anything to do with my problem, was that a week or so before the noise first appeared, I flushed and refilled my loop. I didn't use any cleaner to remove the old coolant, just distilled water and repeated several times until coolant turned clear, nearly like water. Then opened a sealed container I had in storage that was already about 17 months old but that shouldn't have been a problem as it clearly states it has a 2 year shelf life and poured it in. I've been using XSPC's EC6 Opaque White since the system rebuild back in 2021/05. Then a week later I got the noise and you know the rest. Well it's been noise-free for a good two months and actually, the last time it sounded like it was falling apart, the noise went away instantly, no fading no nothing. What I think was happening was probably coolant clogs traveling through the loop and eventually slapping against the impeller, or should I say the impeller slapping the clogs, making that noise. Looks like the impeller survived and likely broke the clogs to pieces eventually, small enough to finally go through without being hit. I believe the reason the noise used to come back is that the clogs probably needed to take enough hits to dissolve. Until that happened, they somehow managed to squeeze through, probably getting stuck at one of many restriction points along the way and therefore wouldn't return to the impeller until days later. Until that last time they probably took the final hit. Felt the need to get back to you, and Corsair, and say that the pump is not faulty. It doesn't appear faulty anyway. I'm 99% sure it was the coolant, although I would blame myself too as I think I didn't flush in time and that type of coolants require more frequent flushes than the clear type, but unfortunately I had so many things going on at the time I failed to do so. Anyway, it's all good now, but just for peace of mind, I've ordered cleaners and dissolvents and I'm gonna do a thorough flush this time in a couple of weeks. Meanwhile, I stress tested the CPU yesterday to see if temps are normal, which would be an indication of good coolant flow. I think it looks good but I could use your opinion. This is after about an hour playing an 8K video, with an average 90% CPU load (82-97% range). I needed an 8K video so I could reach a sustained >82% CPU load, which is only 20% at 4K. The GPU supports up to 4K so the 8K video scaled down to 4K (although it still loaded as 8K on youtube) and that caused it to freeze every few seconds. While frozen, GPU load went down so it had a few seconds to cool down until it resumed, so I'm sure a full GPU stress test would exceed 50C, although not by much I think. So for now ignore the GPU temps, this test is only about the CPU and coolant temps. Took the screenshot when coolant temp nearly stabilized. Ambient 24C. And here it is 30 mins after letting it idle, to see how much time it takes to cool down. Again, took the screenshot when coolant temp nearly stabilized. Here's a bit of iCUE info. I'm using my hottest CPU core as my sensor with the following curves: Pump set at 3200rpm all the way to 50C and then 4000rpm at 60C and 4800 (full speed) at 70C, which essentially means it should never run beyond 4000rpm unless something's wrong. It also means it always runs smooth and steady as 57C is the highest I've seen, so it runs within a 400rpm range essentially and that was deliberate. Fans are set to 750rpm all the way to 50C and then 950rpm at 60C and 1150rpm (full speed) at 70C so it's pretty much the same curve as the pump, meaning they too run within a 100rpm range most of the time, no matter the load. All seem normal? Have anything to suggest?