Question Watercooling D5 pumps in series...loop order?

thilanliyan

Lifer
Jun 21, 2005
11,373
1,226
126
I'm thinking of running 2 D5 Vario pumps in series (for redundancy). I already have the 2nd D5 pump.

My question is, does it matter where in the loop I put the 2nd pump? The first pump will stay attached to the XSPC D5 bay-res I have. The 2nd one I can put anywhere.

Does it make sense to put one pump somewhere halfway through the loop, or maybe just before my 2 GPU blocks? Or right after the 1st pump?
 

aigomorla

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
19,304
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126
no flow is uniform but pressure isnt.

So unless you have something really restrictive, and need to push the water though with more force, it will not matter where you place the pump as flow is uniform in a closed loop.
Flow determines the efficiency of the system, more flow, the better holding capacity of water has, until it reaches a point of diminished returns which is roughly at around 2.75-3gpm.... roughly having 3 x D5 in a series is where u go into horrible diminished returns without active refridgerant.

Most ideally in a redundant system you would probably want it right after the first pump to double the head pressure at maximum and give you the most pressure exiting for bleeding reasons, however if there is no spot for it, do not worry and lose sleep over it, and instead go for the shortest route approach, as the shortest route is always the best route.

So something like Res -> Pump 1 -> Pump 2 -> Waterblock -> Radiator as the waterblock is probably where you have the most to gain from pressure due to turbulance and injector jets.

Also loop order does not matter when you get into 2 x D5's as pretty much you have bolstered your heat capacity tollerance to about 500-600W of heat required for 1C increase, @ ~2.75-3.25gpm flow (aprox). As you can see, unless your running SLI 2080Ti with a TR 3990X in the same loop, your probably not going to get anywhere near that number so temperature thoughout the loop will probably be within 1C at start and finish.

Water needing to stay in radiator to cool down is a myth, as water needs to pass though the radaitor at faster turnover (more flow) is far more efficient and better then leaving it there and forming a temperature gradiatant thoughout the loop (low flow).
 
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Stuka87

Diamond Member
Dec 10, 2010
5,555
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I am not really familiar with those pumps, but will they function as a pass through if not powered? Or will a failed one act as a restriction that would significantly impact water flow?
 

Ajay

Lifer
Jan 8, 2001
10,574
4,516
136
Parallel gives real redundancy, with back flow preventer valves. Kind of over kill though for a PC system.
 

Stuka87

Diamond Member
Dec 10, 2010
5,555
1,344
136
Parallel gives real redundancy, with back flow preventer valves. Kind of over kill though for a PC system.
This is what I think of when I think of redundant. Having them in series makes more sense for a really long loop that needs the extra pushing power, and half the loop between them.

I feel if this is a system that can never go down, it should probably be air cooled. If it is not a 24/7 system, then it can be setup to shutdown if temps get too high, like when a pump fails.
 

thilanliyan

Lifer
Jun 21, 2005
11,373
1,226
126
I am not really familiar with those pumps, but will they function as a pass through if not powered? Or will a failed one act as a restriction that would significantly impact water flow?
Yes, it will pump through fine if in series...I believe Martin's Liquid Lab tested this. If in parallel, unless you have backflow restrictors it will try to pump through the dead pump.
 

thilanliyan

Lifer
Jun 21, 2005
11,373
1,226
126
no flow is uniform but pressure isnt.

So unless you have something really restrictive, and need to push the water though with more force, it will not matter where you place the pump as flow is uniform in a closed loop.
Flow determines the efficiency of the system, more flow, the better holding capacity of water has, until it reaches a point of diminished returns which is roughly at around 2.75-3gpm.... roughly having 3 x D5 in a series is where u go into horrible diminished returns without active refridgerant.

Most ideally in a redundant system you would probably want it right after the first pump to double the head pressure at maximum and give you the most pressure exiting for bleeding reasons, however if there is no spot for it, do not worry and lose sleep over it, and instead go for the shortest route approach, as the shortest route is always the best route.

So something like Res -> Pump 1 -> Pump 2 -> Waterblock -> Radiator as the waterblock is probably where you have the most to gain from pressure due to turbulance and injector jets.

Also loop order does not matter when you get into 2 x D5's as pretty much you have bolstered your heat capacity tollerance to about 500-600W of heat required for 1C increase, @ ~2.75-3.25gpm flow (aprox). As you can see, unless your running SLI 2080Ti with a TR 3990X in the same loop, your probably not going to get anywhere near that number so temperature thoughout the loop will probably be within 1C at start and finish.

Water needing to stay in radiator to cool down is a myth, as water needs to pass though the radaitor at faster turnover (more flow) is far more efficient and better then leaving it there and forming a temperature gradiatant thoughout the loop (low flow).
Thank you for the detailed answer. I will try to put the pump one after the other.

This will be cooling a Ryzen 3600 (for now, until Ryzen 4 comes and then I'll get something more powerful) and 2 Vegas. Loop has an EK Supremacy, 2 EK VGA Supremacy, 1x 280 slim rad, 1x 240 thick rad, 1x 120 slim rad and a XSPC D5 bay-res in it.

One other question I had, how do you "match" the pumps so one isn't pushing against the other? They are both D5 Varios (one is 6yrs old now) but I'm guessing the speed would not be exact even if I set the knob to the same? And actually they are not using the same pump tops so pressure would definitely be different even set to the same speed.

To match the pump outputs, could I say turn up the 2nd pump until it starves a bit then back down in speed until it's no longer starving?
 
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thesmokingman

Platinum Member
May 6, 2010
2,307
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106
One other question I had, how do you "match" the pumps so one isn't pushing against the other? They are both D5 Varios (one is 6yrs old now) but I'm guessing the speed would not be exact even if I set the knob to the same? And actually they are not using the same pump tops so pressure would definitely be different even set to the same speed.

To match the pump outputs, could I say turn up the 2nd pump until it starves a bit then back down in speed until it's no longer starving?
They don't push against the other, they become one. And ideally look for a dual mount. If you don't use a dual mount then you can take advantage of restrictive points in your loop and stick a pump there. Otherwise they work together in unison in series.


As for different pumps and when we talk about watercooling it doesn't matter since the main pumps DDC and D5 are centrifugal pumps. If one dies water will still flow and the pressure drop is not bad.

I also chose two different pumps so I could more closely examine the result of pumps in series and parallel vs the single pump results. In the end, the two mixed pumps worked perfectly together, and the test results using two different pumps did find some interesting details out for me particularly the parallel test results.


parallel = bad
The result was somewhat as expected (Very Poor), but there are some interesting oddities. When you run two pumps in parallel, the curves somewhat get stacked in the X or flow rate direction with an averaging of pressure. Unfortunately this means the real gains of parallel don’t happen until you get beyond the useful restriction range of water cooling loops. On a very high restriction loop you actually don’t gain anything at all. The parallel curve crosses the single DDC curve at about the same point. On a low restriction setup you would see some gains, roughly a 22% increase in pressure, but not at all what you might have hoped for. Parallel simply doesn’t show benefits for the higher restriction levels that we typically see in water cooling and that holds true for pretty much any typical water cooling pump.
 
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aigomorla

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
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I am not really familiar with those pumps,
o_O

Laing D5 is aka the real workhorse or Gold standard of CLC system. The Second being again Laing DDC.
The Black one is the D5... the Silver One is the rolls royce of LCS called the Iwaki RD-30... not many people use it, because it was just too much of a pump for any reasonable LCS, but you know me... im the president of #MOAR EVERYTHING
IMG_0659.JPG

The other gold standard was the DDC...
IMG_1282.JPG

They have a smaller footprint, but they are noticibly louder with a high pitched Whine.
So people who want absolute silence do not use them.
However the DDC are more tuned for waterblock with head pressure.

If you ask me what i use:
I use both a dual D5, and the ban hammer errr a dual DDC intergrated option where the top allows 2 pumps be attached via serial.
IMG_0777.JPG

These guys come either pump only, or with intigrated reservior. You can see my custom tube config... the pump module looks like this tho:
IMG_0771.JPG

The built in Res versions look like this:
IMG_0769.JPG

There are pumps mounted to each side, and the middle allows a passthough.
 

thilanliyan

Lifer
Jun 21, 2005
11,373
1,226
126
They don't push against the other, they become one. And ideally look for a dual mount. If you don't use a dual mount then you can take advantage of restrictive points in your loop and stick a pump there. Otherwise they work together in unison in series.
I thought I read somewhere that having the pumps at difference speeds can negatively effect one of them. Say the 2nd one is running slower than the 1st, so the 1st is having to "push" against the impeller of the 2nd.

Is that BS or does that actually happen?
 

thesmokingman

Platinum Member
May 6, 2010
2,307
230
106
I thought I read somewhere that having the pumps at difference speeds can negatively effect one of them. Say the 2nd one is running slower than the 1st, so the 1st is having to "push" against the impeller of the 2nd.

Is that BS or does that actually happen?
Think of it like a tug of war, and the guy in front of you isn't as strong. It doesn't impede your strength. And as Martin's testing showed, even using two diametrically opposed pumps, one high head pressure and one low head pressure and yet they "worked perfectly together."

I also chose two different pumps so I could more closely examine the result of pumps in series and parallel vs the single pump results. In the end, the two mixed pumps worked perfectly together
 

thilanliyan

Lifer
Jun 21, 2005
11,373
1,226
126
Think of it like a tug of war, and the guy in front of you isn't as strong. It doesn't impede your strength. And as Martin's testing showed, even using two diametrically opposed pumps, one high head pressure and one low head pressure and yet they "worked perfectly together."
Understood. Thanks very much for the clarification.

I did buy an Aquacomputer mechanical flow meter as well and will have 5 D5 tops (stock Laing, XSPC D5 Bayres, Darkside D5, Aquacomputer Ultitop, Singularity Protium D5) to test so I will post a comparison when I get a chance.

I went a bit overboard buying parts lol.
 

aigomorla

Cases and Cooling Mod PC Gaming Mod Elite Member
Super Moderator
Sep 28, 2005
19,304
1,658
126
I thought I read somewhere that having the pumps at difference speeds can negatively effect one of them. Say the 2nd one is running slower than the 1st, so the 1st is having to "push" against the impeller of the 2nd.

Is that BS or does that actually happen?
it can wear out the pump housing on the weaker pump if it exceeds to rated rpms as it will cause the impeller to spin faster then designed.
This is why its highly advised against mis matching pumps.

But if its both d5's and one is set at 3 the other 5, it wouldn't matter.

I went a bit overboard buying parts lol.
Baah no such thing.... *looks away whistling.*
 
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thilanliyan

Lifer
Jun 21, 2005
11,373
1,226
126
it can wear out the pump housing on the weaker pump if it exceeds to rated rpms as it will cause the impeller to spin faster then designed.
This is why its highly advised against mis matching pumps.

But if its both d5's and one is set at 3 the other 5, it wouldn't matter.

Baah no such thing.... *looks away whistling.*
Ah okay, yeah that makes sense about mixing pumps. I'll set both D5s to roughly the same speed and not worry about it.

Lol, yeah I've seen some of your watercooling collection on these forums :D

I wasn't even going to get all those D5 tops, but after buying the Darkside D5 top and inspecting the inside, the machining left a lot to be desired (on top of having 90 degree turns for the outlet), and it wasn't cheap here in Canada either, and I couldn't return it! It didn't leak though from the little testing I did. So then I ordered the Aquacomputer Ultitop to use instead of the Darkside top. Then I decided to change out the XSPX D5 bayres, so I needed another top to replace that one, so I ended up with the Protium D5 as well. I'm going to try and do a physical comparison (inside and outside) of the tops prior to doing the flow tests...hopefully I can post a video.
 

koala-t

Junior Member
Dec 8, 2020
3
1
36
no flow is uniform but pressure isnt.

So unless you have something really restrictive, and need to push the water though with more force, it will not matter where you place the pump as flow is uniform in a closed loop.
Flow determines the efficiency of the system, more flow, the better holding capacity of water has, until it reaches a point of diminished returns which is roughly at around 2.75-3gpm.... roughly having 3 x D5 in a series is where u go into horrible diminished returns without active refridgerant.

Most ideally in a redundant system you would probably want it right after the first pump to double the head pressure at maximum and give you the most pressure exiting for bleeding reasons, however if there is no spot for it, do not worry and lose sleep over it, and instead go for the shortest route approach, as the shortest route is always the best route.

So something like Res -> Pump 1 -> Pump 2 -> Waterblock -> Radiator as the waterblock is probably where you have the most to gain from pressure due to turbulance and injector jets.

Also loop order does not matter when you get into 2 x D5's as pretty much you have bolstered your heat capacity tollerance to about 500-600W of heat required for 1C increase, @ ~2.75-3.25gpm flow (aprox). As you can see, unless your running SLI 2080Ti with a TR 3990X in the same loop, your probably not going to get anywhere near that number so temperature thoughout the loop will probably be within 1C at start and finish.

Water needing to stay in radiator to cool down is a myth, as water needs to pass though the radaitor at faster turnover (more flow) is far more efficient and better then leaving it there and forming a temperature gradiatant thoughout the loop (low flow).

I recently upgraded my loop with a new pump / reservoir combo and gpu block and ran into major flow rate issues. My component temps are approaching near air-cooled temps while the liquid temps stay really, really low even when my single D5 pump is at max. I was doing some research and found this thread and signed up just to say thank you. This was very helpful. I sort of understood the mechanics of adding a second pump into the loop but your post confirmed it.

Prior to the upgrade I was seeing excellent component and liquid temps but alas adding new blocks and res + new loop layout has seemingly maxed out my D5's ability to move water effectively through the blocks. The flow or pressure is so bad that its become increasingly difficult to bleed the loop even with max pump speeds and tilting my case.

I've ordered another d5 pump and plan to place it immediately after the pump/res combo. Hoping that is enough to overcome the restrictive nature of my loop (1x hardware labs gtx 360, 1x EK XE 360, 1x Hardware Labs GTS 480, 1 optimus PC AM4 block, Bitspower FE 3090 block, + 5x 90-degree fittings and a few long runs).

Edit: I should add that I spent a total of 12 hours disassembling the loop and testing each and every component to see where the point of "failure" was. I disassembled water blocks and reseated with new thermal paste, tested my previous pump / res with a single rad, dual rad, and triple rad setups, completely rinsed out my radiators with warm water then finished with distilled water. All this to come to the conclusion that my loop is restrictive and in its current guise a single D5 isn't sufficient for keeping component temps in check for overclocking.
 
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