Water Cool RTX 4090 + i9 13900K Questions

I have built a new PC and I am thinking about investing in a custom water cooling solution to include the GPU. I'm wondering if starting with the Corsair Hydro X Series XH305i custom kit would be wise.. I would add a 420mm radiator in the front of my case. So I'd have a 360mm radiator and a 420mm radiator. Would I need a bigger reservoir or a stronger pump to accommodate this? I also imagine I'll have to source the GPU water block outside of Micro Center. 

PC Specs:
CPU: Intel i9 13900K
Motherboard: ASUS ROG Strix Z790-E
RAM: G.Skill Trident Z5 16GB (x4 = 64GB)
GPU: ZOTAC Gaming RTX 4090 AMP Extreme Airo
PSU: EVGA 1300W P+
AIO: Lian Li Galahad (this would be removed obviously)
Case: ASUS ROG Strix Helios
Fans: 3x Lian Li SL140 (Front), 3x Lian Li SL120 Infinity (Top), 1x Lian Li SL140 (Rear) 
Storage: 2TB Samsung 990 Pro M.2 

Best Answers

  • PowerSpec_MikeW
    PowerSpec_MikeW PowerSpec Engineer
    5 Insightfuls First Anniversary First Comment 5 Awesomes
    Answer ✓


    The Corsair kit is pretty solid component wise. Price is a little high for the components, but Corsair is a premium brand and you get what you pay for. It's a D5 pump, 1500 liters an hour, should keep up. At the extreme side, you might go with two loops, one for the GPU one for the CPU.

    Reservoir, doesn't matter. Looks really. Reservoir's make it easier to fill and especially to bleed air out of the system, but they don't effect performance they're not required. You can fill through a T-Line, but it's really annoying to bleed air out. Where as a reservoir basically will do that automatically over time.

    If you're adding a the GPU, you're going to want a full cover block. Keep in mind these are specific to the card. The only ones I've seen are for the Founders Edition. AIB's change the PCB design, even if it's the same model, the block built for the Founders probably won't fit on the Zotac card.

    Even if you don't do the GPU, the 13900K with a 360 or 420MM is worth it. PL2 is 253W, and manufacturers usually set the board limit at 4096W. It'll draw as much power as you can dissipate. Even with a 420MM rad on a custom loop, if you run Cinebench R23 Multi-Core it'll hit and sit on 100C. You'll probably be at 5+Ghz and pulling 300+ watts. Better the cooling, better the overall performance. Overclocking is undervolting.

  • PowerSpec_MikeW
    PowerSpec_MikeW PowerSpec Engineer
    5 Insightfuls First Anniversary First Comment 5 Awesomes
    Answer ✓


    Two loops would mean two pumps. You'd want two reservoir's as well. So you'd just get another D5 pump/res combo like you have on the Corsair kit. Add your 420MM rad, tubes, fittings and you're good to go.


  • TKE228


    First of all, thank you for the very detailed and quick response!

    I think you've convinced me to go this route. I'm thinking I should buy the Corsair kit and an additional Corsair 420mm rad. The kit supposedly comes with additional fittings to add in a GPU water block.

    EK appears to have a full water block for my Zotac GPU. Then I guess I would want to look at water line diameter and fitting size and make sure I can get the water lines actually mated properly to the block..

    When you talk about having separate 'loops', are you meaning to have two separate pumps? I would imagine then I could have two pumps run off of the same reservoir. Each pump running to a separate 'loop' or component block. Now that could get interesting (especially considering the primary reason I started thinking about this project is to use up more space in the case; this Helios is HUGE and has a bunch of empty space towards the front).

  • Rs199208

    there is no reason to run dual loops for cpu/gpu cooling. it's actually much better to run one loop because rarely will you ever have both the cpu and gpu maxed out at the same time if ever.

    myself, I've never had a cpu and gpu maxed out at the same time yet...

    for instance: cpu benchmarking will run the cpu at 100% load but no use for the gpu.

    in gaming the gpu will carry the majority of the load not the cpu unless running low resolution or a badly optimized game and even then the gpu will reduce load in that scenario as the cpu will increase load.

    you could actually have more difficulty cooling a 13900k than a 4090 depending on the workload so you'll want all the rads then on the cpu loop.

    the only reason people dual loop are for looks. having multiple reservoirs, cool hard tubing running everywhere with cool coloring in the loops.

    that said there is one scenario where a dual loop makes sense and I'm actually going to reconfigure my loop into this version: one loop for the cpu/gpu, and one loop for the ram because of high overclocking to more easily stabilize with the highest performance settings like dram speed and tightened timings. this isn't needed for the majority of rigs. in my scenario i run external loops, all my rads are outside of the case so its much easier and purely for performance not looks. since i want my DDR5 to run cooler for stabilization i don't want the other components raising the loop temperatures when they are running their hottest. cpu/gpu doesn't need that kind of over the top heat consideration.

    now onto the 64GB of DDR5? that's really difficult to get stable and even more difficult with 4 sticks instead of 2. you can't go very high clocks with 64GB and some motherboards require tweaking of the ram settings to get it to run at XMP if capable at all depending on the speeds. so check the MB QVL, even then its not a guarantee the kit will work as intended..

  • Rs199208

    i just checked your MB choice for 4 sticks of ddr5 compatibility and no 4x setup is listed as compatible yet. this doesn't mean you can't get 4 sticks to run any XMP it just means Asus currently doesn't back any 4 stick configuration, you are on your own.

We love seeing what our customers build

Submit photos and a description of your PC to our build showcase

Submit Now
Looking for a little inspiration?

See other custom PC builds and get some ideas for what can be done

View Build Showcase


If You Can Dream it, We Can Build it.

Services starting at $149.99