Do I Need 2 Pumps?

You don't need two pumps for that; a single D5 or DDC will suffice.

To determine if you need two pumps you can plug your loop (or as close as you can get it) into Martin's pump and radiator optimiser. In this case I know that a D5 / DDC can handle a CPU / GPU / 2 Rad loop. The RAM block won't help, but it won't hurt too much.

You can also run two pumps for redundancy even if you don't ned them for flow rates.

You don't need two pumps for that.

But still, you should buy two but that is my overkilled opinion.

(Two pumps is also good for redundancy if one fail, you still have one temporary, but also two pumps is future proof, I was happy to have my two pumps when I decided to throw 3 more blocks and one Quad radiator in my loop.)

Go for two pumps in serial (single loop) with a Dual top




IF YOU WANT A FLOW RATE CALCULATOR
go here, Martin's Liquid lab creation.

http://martinsliquidlab.org/pump-and-radiator-optimizer-spreadsheet/

Read it and download it, I don't know how it works, I just know it exists.

Good Luck



PS : About your second post, this is how they are set-up in my rig. maximize the picture for better view


Edited by KaRLiToS - 8/27/12 at 4:30pm

You would run them in series, never parallel.

You can get dual pump tops or just plumb them "manually". Some people separate the pumps in the loop, e.g.

res>pump1>block>rad>pump2>block>rad>res

Either way is fine, just try not to have the pump outlet going directly into the res.

Hahaha, its still better to mention it just in case
More information is always better.

one pump could work as long as you run the tubing right. if you run the blocks in parallel instead of series the resistance drops by half. blocks can be restrictive.

im running a swiftech 655b pump they advertise it as usable for "extreme cooling situations" but i dont think its really strong enough for much more than the triple 120mm rad and the phyobia dual bay reservoir i have. i mean its working fine but its not overkill enough. i mean wouldn't it be cool to actually need stainless steel braided hoses in your pc. just playin

Parallel:



With parallel the flow rate is shared between the components and the overall restriction is halved (assuming that the components are the same design). One potential issue is if you run a high restriction and a low restriction component in parallel most of the flow will go through the low restriction component. This creates problems with flow balancing.

Some people run their GPU blocks in parallel to reduce the overall loop restriction. Parallel GPU blocks improves the flow rate through other components like the CPU block. As GPU blocks are not all that sensitive to flow rate compared to CPU blocks it is a trade off between a slight rise in GPU temperature compared to a larger drop in CPU temperature.



Series:


With serial the flow rate is the same through all components and the overall restrition is summed. Serial removes any issues that might arise with flow balancing and makes things simpler. Most people plumb their loop in series.

With pumps it is important to plumb them in series. The flow rate of a loop is determined by how hard it is to push water through components, something usually referred to as restriction. Restriction is overcome by pressure - the higher the pressure at the pump outlet the faster the water can flow through the loop.

Under normal operation series provides higher pressure which overcomes the restriction to provide higher flow rates.. Putting pumps in series does not provide higher flow rates as the pressure stays roughly the same.

If one pump were to fail in series then the water will continue to flow normally, albeit with reduced flow rates. In parallel the water will recirculate through the stopped pump, dramatically reducing the loop flow rate. Because of this pumps in series can be said to double your reliability whereas parallel halves it.
Edited by GingerJohn - 8/28/12 at 1:59pm