Water Cooling Dual Pump - Location of 2nd Pump

[AndroTest]

Here's what I have

3x GPU, 1 CPU, 2x 480 Rads, 1x 240rad, 1000D case.

I have one pump+res combo and one pump only. Which one should I do:

1) res/pump -> 2nd pump -> rad 480 #1 -> rad 480 #2 -> CPU -> rad 240 -> GPU #1 -> GPU #2 -> GPU #3 -> res/pump

2) res/pump -> rad 480 #1 -> rad 480 #2 -> CPU -> 2nd pump -> rad 240 -> GPU #1 -> GPU #2 -> GPU #3 -> res/pump

or some other order?

I ask because in any of these cases, when I initially fill the water in pump/res, first pump/res is covered, but till it gets water to 2nd pump, it will run dry for couple seconds and I hear that its a big no no. So what's the solution here? Should I manually first unplug the 2nd pump (turn it off) till whole loop is filled and then turn on the 2nd one? Or I shouldn't worry about couple seconds?

 

[bmwbaxter]

Order doesn't matter IMO. Put the second pump below the pump res so it won't run dry and just fill the loop with the pump res powered only.

 

[AndroTest]

Unfortunately my setup somehow can't have the 2nd pump below pump/res, long story.

But if I keep the 2nd pump not powered, water will just flow through it, correct? I can turn it on once I have water in the whole loop, correct?

Also to confirm, the 2nd pump location in the loop almost absolutely doesn't matter at all, correct?

 

[bmwbaxter]

Its a closed system, so order doesn't matter.

 

[Voodoo Rufus]

As stated, order doesn't matter. Just mount the pumps where it makes the most sense for your tubing runs. In my system that happened to be with my second pump half way through the loop. Since your second pump isn't below the reservoir, just leave it unplugged as you fill the system to prime it with your res-pump. Once you force enough fluid through it, then you can turn it on to help with bleeding.

 

[EarthDog]

Loop order only matters in that you should have a res before the pump. Outside of that it shouldn't matter. Your most difficult part in this is making sure the second pump is primed when you start to fill the system. Id either find a res/pump combo again, or put the second pump immediately after the first. You should be able to get away with a couple of seconds, but.........I wouldn't push it.